[PATCH 09/12] Do not compact within a preferred zone after a compaction failure
Mel Gorman
fragmentation, a compaction run complete and an allocation failure still
fail. There are two obvious reasons as to why
o Page migration cannot move all pages so fragmentation remains
o A suitable page may exist but watermarks are not met
In the event of compaction and allocation failure, this patch prevents
compaction happening for a short interval. It's only recorded on the
preferred zone but that should be enough coverage. This could have been
implemented similar to the zonelist_cache but the increased size of the
zonelist did not appear to be justified.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
include/linux/compaction.h | 29 +++++++++++++++++++++++++++++
include/linux/mmzone.h | 7 +++++++
mm/page_alloc.c | 5 ++++-
3 files changed, 40 insertions(+), 1 deletions(-)
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 1cf95e2..1891bd1 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -13,6 +13,26 @@ extern int sysctl_compaction_handler(struct ctl_table *table, int write,
extern int fragmentation_index(struct zone *zone, unsigned int order);
extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *mask);
+
+/* defer_compaction - Do not compact within a zone until a given time */
+static inline void defer_compaction(struct zone *zone, unsigned long resume)
+{
+ /*
+ * This function is called when compaction fails to result in a page
+ * allocation success. This is somewhat unsatisfactory as the failure
+ * to compact has nothing to do with time and everything to do with
+ * the requested order, the number of free pages and watermarks. How
+ * to wait on that is more unclear, but the answer would apply to
+ * other areas where the VM waits based on time.
+ */
+ zone->compact_resume = jiffies + HZ/50;
+}
+
+static inline int compaction_deferred(struct zone *zone)
+{
+ return time_before(jiffies, zone->compact_resume);
+}
+
#else
static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask)
@@ -20,6 +40,15 @@ static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
return COMPACT_INCOMPLETE;
}
+static inline void defer_compaction(struct zone *zone, unsigned long resume)
+{
+}
+
+static inline int compaction_deferred(struct zone *zone)
+{
+ return 1;
+}
+
#endif /* CONFIG_COMPACTION */
#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 30fe668..31fb38b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -328,6 +328,13 @@ struct zone {
unsigned long *pageblock_flags;
#endif /* CONFIG_SPARSEMEM */
+#ifdef CONFIG_COMPACTION
+ /*
+ * If a compaction fails, do not try compaction again until
+ * jiffies is after the value of compact_resume
+ */
+ unsigned long compact_resume;
+#endif
ZONE_PADDING(_pad1_)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1910b8b..7021c68 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1730,7 +1730,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
cond_resched();
/* Try memory compaction for high-order allocations before reclaim */
- if (order) {
+ if (order && !compaction_deferred(preferred_zone)) {
*did_some_progress = try_to_compact_pages(zonelist,
order, gfp_mask, nodemask);
if (*did_some_progress != COMPACT_INCOMPLETE) {
@@ -1750,6 +1750,9 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
*/
count_vm_event(COMPACTFAIL);
+ /* On failure, avoid compaction for a short time. */
+ defer_compaction(preferred_zone, jiffies + HZ/50);
+
cond_resched();
}
}
--
1.6.5
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Mel Gorman
written to, each zone in that node is compacted. The intention that this
would be used by something like a job scheduler in a batch system before
a job starts so that the job can allocate the maximum number of
hugepages without significant start-up cost.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
drivers/base/node.c | 3 +++
include/linux/compaction.h | 16 ++++++++++++++++
mm/compaction.c | 23 +++++++++++++++++++++++
3 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 7012279..2333c9d 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -15,6 +15,7 @@
#include <linux/cpu.h>
#include <linux/device.h>
#include <linux/swap.h>
+#include <linux/compaction.h>
static struct sysdev_class node_class = {
.name = "node",
@@ -239,6 +240,8 @@ int register_node(struct node *node, int num, struct node *parent)
scan_unevictable_register_node(node);
hugetlb_register_node(node);
+
+ compaction_register_node(node);
}
return error;
}
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index facaa3d..6a2eefd 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -10,4 +10,20 @@ extern int sysctl_compaction_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos);
#endif /* CONFIG_COMPACTION */
+#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+extern int compaction_register_node(struct node *node);
+extern void compaction_unregister_node(struct node *node);
+
+#else
+
+static inline int compaction_register_node(struct node *node)
+{
+ return 0;
+}
+
+static inline void compaction_unregister_node(struct node *node)
+{
+}
+#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
+
#endif /* _LINUX_COMPACTION_H */
diff --git a/mm/compaction.c b/mm/compaction.c
index c0b9dc9..f5bd5ed 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -12,6 +12,7 @@
#include <linux/compaction.h>
#include <linux/mm_inline.h>
#include <linux/sysctl.h>
+#include <linux/sysfs.h>
#include "internal.h"
/*
@@ -399,3 +400,25 @@ int sysctl_compaction_handler(struct ctl_table *table, int write,
return 0;
}
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+ssize_t sysfs_compact_node(struct sys_device *dev,
+ struct sysdev_attribute *attr,
+ const char *buf, size_t count)
+{
+ compact_node(dev->id);
+
+ return count;
+}
+static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
+
+int compaction_register_node(struct node *node)
+{
+ return sysdev_create_file(&node->sysdev, &attr_compact);
+}
+
+void compaction_unregister_node(struct node *node)
+{
+ return sysdev_remove_file(&node->sysdev, &attr_compact);
+}
+#endif /* CONFIG_SYSFS && CONFIG_NUMA */
Mel Gorman
page migration under heavy load on pages that do not belong to the process
doing the migration - e.g. during memory compaction. The bug triggered is
a NULL pointer deference in list_for_each_entry().
I believe what is happening is that rmap_walk() is called but the process
exits before the lock gets taken. rmap_walk_anon() by design is not holding
the mmap_sem which would have guaranteed its existance. There is a comment
explaining the locking (or lack thereof) decision but the reasoning is not
very clear.
This patch checks if the VMA list is empty after the lock is taken which
avoids the race. It should be reviewed by people more familiar with
migration to confirm this is a sufficient or if the locking decisions
around rmap_walk() need to be revisited.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
mm/rmap.c | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 278cd27..b468d5f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1237,6 +1237,14 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
if (!anon_vma)
return ret;
spin_lock(&anon_vma->lock);
+
+ /*
+ * While the anon_vma may still exist, there is no guarantee
+ * the VMAs still do.
+ */
+ if (list_empty(&anon_vma->head))
+ goto out_anon_unlock;
+
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
unsigned long address = vma_address(page, vma);
if (address == -EFAULT)
@@ -1245,6 +1253,8 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
if (ret != SWAP_AGAIN)
break;
}
+
+out_anon_unlock:
spin_unlock(&anon_vma->lock);
return ret;
Mel Gorman
being able to hot-remove memory. The main users of page migration such as
sys_move_pages(), sys_migrate_pages() and cpuset process migration are
only beneficial on NUMA so it makes sense.
As memory compaction will operate within a zone and is useful on both NUMA
and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the
user selects CONFIG_COMPACTION as an option.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Reviewed-by: Christoph Lameter <c...@linux-foundation.org>
---
mm/Kconfig | 20 ++++++++++++++++----
1 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index 17b8947..b1c2781 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -168,17 +168,29 @@ config SPLIT_PTLOCK_CPUS
default "4"
#
+# support for memory compaction
+config COMPACTION
+ bool "Allow for memory compaction"
+ def_bool y
+ select MIGRATION
+ depends on EXPERIMENTAL && HUGETLBFS
+ help
+ Allows the compaction of memory for the allocation of huge pages.
+
+#
# support for page migration
#
config MIGRATION
bool "Page migration"
def_bool y
- depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
+ depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
help
Allows the migration of the physical location of pages of processes
- while the virtual addresses are not changed. This is useful for
- example on NUMA systems to put pages nearer to the processors accessing
- the page.
+ while the virtual addresses are not changed. This is useful in
+ two situations. The first is on NUMA systems to put pages nearer
+ to the processors accessing. The second is when allocating huge
+ pages as migration can relocate pages to satisfy a huge page
+ allocation instead of reclaiming.
config PHYS_ADDR_T_64BIT
def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
Mel Gorman
relocating movable pages towards the end of the zone.
A single compaction run involves a migration scanner and a free scanner.
Both scanners operate on pageblock-sized areas in the zone. The migration
scanner starts at the bottom of the zone and searches for all movable pages
within each area, isolating them onto a private list called migratelist.
The free scanner starts at the top of the zone and searches for suitable
areas and consumes the free pages within making them available for the
migration scanner. The pages isolated for migration are then migrated to
the newly isolated free pages.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
include/linux/compaction.h | 8 +
include/linux/mm.h | 1 +
include/linux/swap.h | 5 +
include/linux/vmstat.h | 1 +
mm/Makefile | 1 +
mm/compaction.c | 341 ++++++++++++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 37 +++++
mm/vmscan.c | 5 -
mm/vmstat.c | 5 +
scripts/kconfig/conf.c | 1 -
10 files changed, 399 insertions(+), 6 deletions(-)
create mode 100644 include/linux/compaction.h
create mode 100644 mm/compaction.c
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
new file mode 100644
index 0000000..6201371
--- /dev/null
+++ b/include/linux/compaction.h
@@ -0,0 +1,8 @@
+#ifndef _LINUX_COMPACTION_H
+#define _LINUX_COMPACTION_H
+
+/* Return values for compact_zone() */
+#define COMPACT_INCOMPLETE 0
+#define COMPACT_COMPLETE 1
+
+#endif /* _LINUX_COMPACTION_H */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 60c467b..c2a2ede 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -332,6 +332,7 @@ void put_page(struct page *page);
void put_pages_list(struct list_head *pages);
void split_page(struct page *page, unsigned int order);
+int split_free_page(struct page *page);
/*
* Compound pages have a destructor function. Provide a
diff --git a/include/linux/swap.h b/include/linux/swap.h
index a2602a8..7e7181b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -238,6 +238,11 @@ static inline void lru_cache_add_active_file(struct page *page)
__lru_cache_add(page, LRU_ACTIVE_FILE);
}
+/* LRU Isolation modes. */
+#define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
+#define ISOLATE_ACTIVE 1 /* Isolate active pages. */
+#define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
+
/* linux/mm/vmscan.c */
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *mask);
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index ee03bba..d7f7236 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -43,6 +43,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY,
KSWAPD_SKIP_CONGESTION_WAIT,
PAGEOUTRUN, ALLOCSTALL, PGROTATED,
+ COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
#ifdef CONFIG_HUGETLB_PAGE
HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
#endif
diff --git a/mm/Makefile b/mm/Makefile
index 7a68d2a..ccb1f72 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_FAILSLAB) += failslab.o
obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
obj-$(CONFIG_FS_XIP) += filemap_xip.o
obj-$(CONFIG_MIGRATION) += migrate.o
+obj-$(CONFIG_COMPACTION) += compaction.o
obj-$(CONFIG_SMP) += percpu.o
obj-$(CONFIG_QUICKLIST) += quicklist.o
obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
diff --git a/mm/compaction.c b/mm/compaction.c
new file mode 100644
index 0000000..51ec864
--- /dev/null
+++ b/mm/compaction.c
@@ -0,0 +1,341 @@
+/*
+ * linux/mm/compaction.c
+ *
+ * Memory compaction for the reduction of external fragmentation. Note that
+ * this heavily depends upon page migration to do all the real heavy
+ * lifting
+ *
+ * Copyright IBM Corp. 2009 Mel Gorman <m...@csn.ul.ie>
+ */
+#include <linux/swap.h>
+#include <linux/migrate.h>
+#include <linux/compaction.h>
+#include <linux/mm_inline.h>
+#include "internal.h"
+
+/*
+ * compact_control is used to track pages being migrated and the free pages
+ * they are being migrated to during memory compaction. The free_pfn starts
+ * at the end of a zone and migrate_pfn begins at the start. Movable pages
+ * are moved to the end of a zone during a compaction run and the run
+ * completes when free_pfn <= migrate_pfn
+ */
+struct compact_control {
+ struct list_head freepages; /* List of free pages to migrate to */
+ struct list_head migratepages; /* List of pages being migrated */
+ unsigned long nr_freepages; /* Number of isolated free pages */
+ unsigned long nr_migratepages; /* Number of pages to migrate */
+ unsigned long free_pfn; /* isolate_freepages search base */
+ unsigned long migrate_pfn; /* isolate_migratepages search base */
+ struct zone *zone;
+};
+
+static int release_freepages(struct zone *zone, struct list_head *freelist)
+{
+ struct page *page, *next;
+ int count = 0;
+
+ list_for_each_entry_safe(page, next, freelist, lru) {
+ list_del(&page->lru);
+ __free_page(page);
+ count++;
+ }
+
+ return count;
+}
+
+/* Isolate free pages onto a private freelist. Must hold zone->lock */
+static int isolate_freepages_block(struct zone *zone,
+ unsigned long blockpfn,
+ struct list_head *freelist)
+{
+ unsigned long zone_end_pfn, end_pfn;
+ int total_isolated = 0;
+
+ /* Get the last PFN we should scan for free pages at */
+ zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
+ end_pfn = blockpfn + pageblock_nr_pages;
+ if (end_pfn > zone_end_pfn)
+ end_pfn = zone_end_pfn;
+
+ /* Isolate free pages. This assumes the block is valid */
+ for (; blockpfn < end_pfn; blockpfn++) {
+ struct page *page;
+ int isolated, i;
+
+ if (!pfn_valid_within(blockpfn))
+ continue;
+
+ page = pfn_to_page(blockpfn);
+ if (!PageBuddy(page))
+ continue;
+
+ /* Found a free page, break it into order-0 pages */
+ isolated = split_free_page(page);
+ total_isolated += isolated;
+ for (i = 0; i < isolated; i++) {
+ list_add(&page->lru, freelist);
+ page++;
+ }
+ blockpfn += isolated - 1;
+ }
+
+ return total_isolated;
+}
+
+/* Returns 1 if the page is within a block suitable for migration to */
+static int suitable_migration_target(struct page *page)
+{
+ /* If the page is a large free page, then allow migration */
+ if (PageBuddy(page) && page_order(page) >= pageblock_order)
+ return 1;
+
+ /* If the block is MIGRATE_MOVABLE, allow migration */
+ if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)
+ return 1;
+
+ /* Otherwise skip the block */
+ return 0;
+}
+
+/*
+ * Based on information in the current compact_control, find blocks
+ * suitable for isolating free pages from
+ */
+static void isolate_freepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ struct page *page;
+ unsigned long high_pfn, low_pfn, pfn;
+ unsigned long flags;
+ int nr_freepages = cc->nr_freepages;
+ struct list_head *freelist = &cc->freepages;
+
+ pfn = cc->free_pfn;
+ low_pfn = cc->migrate_pfn + pageblock_nr_pages;
+ high_pfn = low_pfn;
+
+ /*
+ * Isolate free pages until enough are available to migrate the
+ * pages on cc->migratepages. We stop searching if the migrate
+ * and free page scanners meet or enough free pages are isolated.
+ */
+ spin_lock_irqsave(&zone->lock, flags);
+ for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
+ pfn -= pageblock_nr_pages) {
+ int isolated;
+
+ if (!pfn_valid(pfn))
+ continue;
+
+ /* Check for overlapping nodes/zones */
+ page = pfn_to_page(pfn);
+ if (page_zone(page) != zone)
+ continue;
+
+ /* Check the block is suitable for migration */
+ if (!suitable_migration_target(page))
+ continue;
+
+ /* Found a block suitable for isolating free pages from */
+ isolated = isolate_freepages_block(zone, pfn, freelist);
+ nr_freepages += isolated;
+
+ /*
+ * Record the highest PFN we isolated pages from. When next
+ * looking for free pages, the search will restart here as
+ * page migration may have returned some pages to the allocator
+ */
+ if (isolated)
+ high_pfn = max(high_pfn, pfn);
+ }
+ spin_unlock_irqrestore(&zone->lock, flags);
+
+ cc->free_pfn = high_pfn;
+ cc->nr_freepages = nr_freepages;
+}
+
+/*
+ * Isolate all pages that can be migrated from the block pointed to by
+ * the migrate scanner within compact_control.
+ */
+static unsigned long isolate_migratepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ unsigned long low_pfn, end_pfn;
+ struct list_head *migratelist;
+ enum lru_list lru_src;
+
+ low_pfn = ALIGN(cc->migrate_pfn, pageblock_nr_pages);
+ migratelist = &cc->migratepages;
+
+ /* Do not scan outside zone boundaries */
+ if (low_pfn < zone->zone_start_pfn)
+ low_pfn = zone->zone_start_pfn;
+
+ /* Setup to scan one block but not past where we are migrating to */
+ end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
+ cc->migrate_pfn = end_pfn;
+ VM_BUG_ON(end_pfn > cc->free_pfn);
+
+ if (!pfn_valid(low_pfn))
+ return 0;
+
+ migrate_prep();
+
+ /* Time to isolate some pages for migration */
+ spin_lock_irq(&zone->lru_lock);
+ for (; low_pfn < end_pfn; low_pfn++) {
+ struct page *page;
+ if (!pfn_valid_within(low_pfn))
+ continue;
+
+ /* Get the page and skip if free */
+ page = pfn_to_page(low_pfn);
+ if (PageBuddy(page)) {
+ low_pfn += (1 << page_order(page)) - 1;
+ continue;
+ }
+
+ if (!PageLRU(page) || PageUnevictable(page))
+ continue;
+
+ /* Try isolate the page */
+ lru_src = page_lru(page);
+ switch (__isolate_lru_page(page, ISOLATE_BOTH, 0)) {
+ case 0:
+ list_move(&page->lru, migratelist);
+ mem_cgroup_del_lru(page);
+ cc->nr_migratepages++;
+ break;
+
+ case -EBUSY:
+ /*
+ * else it is being freed elsewhere. The
+ * problem is that we are not really sure where
+ * it came from in the first place
+ * XXX: Verify the putback logic is ok. This was
+ * all written before LRU lists were split
+ */
+ list_move(&page->lru, &zone->lru[lru_src].list);
+ mem_cgroup_rotate_lru_list(page, page_lru(page));
+ continue;
+
+ default:
+ BUG();
+ }
+ }
+ spin_unlock_irq(&zone->lru_lock);
+
+ return cc->nr_migratepages;
+}
+
+/*
+ * This is a migrate-callback that "allocates" freepages by taking pages
+ * from the isolated freelists in the block we are migrating to.
+ */
+static struct page *compaction_alloc(struct page *migratepage,
+ unsigned long data,
+ int **result)
+{
+ struct compact_control *cc = (struct compact_control *)data;
+ struct page *freepage;
+
+ VM_BUG_ON(cc == NULL);
+
+ /* Isolate free pages if necessary */
+ if (list_empty(&cc->freepages)) {
+ isolate_freepages(cc->zone, cc);
+
+ if (list_empty(&cc->freepages))
+ return NULL;
+ }
+
+ freepage = list_entry(cc->freepages.next, struct page, lru);
+ list_del(&freepage->lru);
+ cc->nr_freepages--;
+
+ return freepage;
+}
+
+/*
+ * We cannot control nr_migratepages and nr_freepages fully when migration is
+ * running as migrate_pages() has no knowledge of compact_control. When
+ * migration is complete, we count the number of pages on the lists by hand.
+ */
+static void update_nr_listpages(struct compact_control *cc)
+{
+ int nr_migratepages = 0;
+ int nr_freepages = 0;
+ struct page *page;
+ list_for_each_entry(page, &cc->migratepages, lru)
+ nr_migratepages++;
+ list_for_each_entry(page, &cc->freepages, lru)
+ nr_freepages++;
+
+ cc->nr_migratepages = nr_migratepages;
+ cc->nr_freepages = nr_freepages;
+}
+
+static inline int compact_finished(struct zone *zone,
+ struct compact_control *cc)
+{
+ /* Compaction run completes if the migrate and free scanner meet */
+ if (cc->free_pfn <= cc->migrate_pfn)
+ return COMPACT_COMPLETE;
+
+ return COMPACT_INCOMPLETE;
+}
+
+static int compact_zone(struct zone *zone, struct compact_control *cc)
+{
+ int ret = COMPACT_INCOMPLETE;
+
+ /*
+ * Setup to move all movable pages to the end of the zone
+ * XXX: This could be improved upon. In the event compaction
+ * is being successful quickly but called often, there
+ * is a likelihood of scanning the same blocks as sources
+ * and targets frequently. Might be worth caching the
+ * last migrate_pfn to reduce scan times.
+ */
+ cc->migrate_pfn = zone->zone_start_pfn;
+ cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
+ cc->free_pfn &= ~(pageblock_nr_pages-1);
+
+ for (; ret == COMPACT_INCOMPLETE; ret = compact_finished(zone, cc)) {
+ unsigned long nr_migrate, nr_remaining;
+ if (!isolate_migratepages(zone, cc))
+ continue;
+
+ nr_migrate = cc->nr_migratepages;
+ migrate_pages(&cc->migratepages, compaction_alloc,
+ (unsigned long)cc, 0);
+ update_nr_listpages(cc);
+ nr_remaining = cc->nr_migratepages;
+
+ count_vm_event(COMPACTBLOCKS);
+ count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
+ if (nr_remaining)
+ count_vm_events(COMPACTPAGEFAILED, nr_remaining);
+ }
+
+ /* Release free pages and check accounting */
+ cc->nr_freepages -= release_freepages(zone, &cc->freepages);
+ VM_BUG_ON(cc->nr_freepages != 0);
+
+ /*
+ * Release LRU pages not migrated
+ * XXX: Page migration at this point tries fairly hard to move
+ * pages as it is but if migration fails, pages are left
+ * on cc->migratepages for more passes. This might cause
+ * multiple useless failures. Watch compact_pagemigrate_failed
+ * in /proc/vmstat. If it grows a lot, then putback should
+ * happen after each failed migration
+ */
+ if (!list_empty(&cc->migratepages))
+ putback_lru_pages(&cc->migratepages);
+
+ return ret;
+}
+
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8deb9d0..6d57154 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1168,6 +1168,43 @@ void split_page(struct page *page, unsigned int order)
set_page_refcounted(page + i);
}
+/* Similar to split_page except the page is already free */
+int split_free_page(struct page *page)
+{
+ unsigned int order;
+ unsigned long watermark;
+ struct zone *zone;
+
+ BUG_ON(!PageBuddy(page));
+
+ zone = page_zone(page);
+ order = page_order(page);
+
+ /* Obey watermarks or the system could deadlock */
+ watermark = low_wmark_pages(zone) + (1 << order);
+ if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+ return 0;
+
+ /* Remove page from free list */
+ list_del(&page->lru);
+ zone->free_area[order].nr_free--;
+ rmv_page_order(page);
+ __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
+
+ /* Split into individual pages */
+ set_page_refcounted(page);
+ split_page(page, order);
+
+ /* Set the migratetype on the assumption it's for migration */
+ if (order >= pageblock_order - 1) {
+ struct page *endpage = page + (1 << order) - 1;
+ for (; page < endpage; page += pageblock_nr_pages)
+ set_pageblock_migratetype(page, MIGRATE_MOVABLE);
+ }
+
+ return 1 << order;
+}
+
/*
* Really, prep_compound_page() should be called from __rmqueue_bulk(). But
* we cheat by calling it from here, in the order > 0 path. Saves a branch
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c26986c..47de19b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -803,11 +803,6 @@ keep:
return nr_reclaimed;
}
-/* LRU Isolation modes. */
-#define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
-#define ISOLATE_ACTIVE 1 /* Isolate active pages. */
-#define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
-
/*
* Attempt to remove the specified page from its LRU. Only take this page
* if it is of the appropriate PageActive status. Pages which are being
diff --git a/mm/vmstat.c b/mm/vmstat.c
index e2d0cc1..f0930ae 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -852,6 +852,11 @@ static const char * const vmstat_text[] = {
"allocstall",
"pgrotated",
+
+ "compact_blocks_moved",
+ "compact_pages_moved",
+ "compact_pagemigrate_failed",
+
#ifdef CONFIG_HUGETLB_PAGE
"htlb_buddy_alloc_success",
"htlb_buddy_alloc_fail",
Mel Gorman
takes the allocation size into account. For the most part, the huge page
size will be the size of interest but not necessarily so it is exported
on a per-order and per-zone basis via /proc/pagetypeinfo.
The index is normally calculated as a value between 0 and 1 which is
obviously unsuitable within the kernel. Instead, the first three decimal
places are used as a value between 0 and 1000 for an integer approximation.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
Documentation/filesystems/proc.txt | 10 ++++
mm/vmstat.c | 99 ++++++++++++++++++++++++++++++++++++
2 files changed, 109 insertions(+), 0 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 1829dfb..0968a81 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -614,6 +614,10 @@ Node 0, zone DMA32, type Movable 169 152 113 91 77
Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
+Unusable free space index at order
+Node 0, zone DMA 0 0 0 2 6 18 34 67 99 227 485
+Node 0, zone DMA32 0 0 1 2 4 7 10 17 23 31 34
+
Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
Node 0, zone DMA 2 0 5 1 0
Node 0, zone DMA32 41 6 967 2 0
@@ -629,6 +633,12 @@ then gives the same type of information as buddyinfo except broken down
by migrate-type and finishes with details on how many page blocks of each
type exist.
+The unusable free space index measures how much of the available free
+memory cannot be used to satisfy an allocation of a given size and is a
+value between 0 and 1000. The higher the value, the more of free memory is
+unusable and by implication, the worse the external fragmentation is. The
+percentage of unusable free memory can be found by dividing this value by 10.
+
If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
make an estimate of the likely number of huge pages that can be allocated
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 6051fba..d05d610 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -451,6 +451,104 @@ static int frag_show(struct seq_file *m, void *arg)
return 0;
}
+
+struct contig_page_info {
+ unsigned long free_pages;
+ unsigned long free_blocks_total;
+ unsigned long free_blocks_suitable;
+};
+
+/*
+ * Calculate the number of free pages in a zone, how many contiguous
+ * pages are free and how many are large enough to satisfy an allocation of
+ * the target size. Note that this function makes to attempt to estimate
+ * how many suitable free blocks there *might* be if MOVABLE pages were
+ * migrated. Calculating that is possible, but expensive and can be
+ * figured out from userspace
+ */
+static void fill_contig_page_info(struct zone *zone,
+ unsigned int suitable_order,
+ struct contig_page_info *info)
+{
+ unsigned int order;
+
+ info->free_pages = 0;
+ info->free_blocks_total = 0;
+ info->free_blocks_suitable = 0;
+
+ for (order = 0; order < MAX_ORDER; order++) {
+ unsigned long blocks;
+
+ /* Count number of free blocks */
+ blocks = zone->free_area[order].nr_free;
+ info->free_blocks_total += blocks;
+
+ /* Count free base pages */
+ info->free_pages += blocks << order;
+
+ /* Count the suitable free blocks */
+ if (order >= suitable_order)
+ info->free_blocks_suitable += blocks <<
+ (order - suitable_order);
+ }
+}
+
+/*
+ * Return an index indicating how much of the available free memory is
+ * unusable for an allocation of the requested size.
+ */
+static int unusable_free_index(struct zone *zone,
+ unsigned int order,
+ struct contig_page_info *info)
+{
+ /* No free memory is interpreted as all free memory is unusable */
+ if (info->free_pages == 0)
+ return 1000;
+
+ /*
+ * Index should be a value between 0 and 1. Return a value to 3
+ * decimal places.
+ *
+ * 0 => no fragmentation
+ * 1 => high fragmentation
+ */
+ return ((info->free_pages - (info->free_blocks_suitable << order)) * 1000) / info->free_pages;
+
+}
+
+static void pagetypeinfo_showunusable_print(struct seq_file *m,
+ pg_data_t *pgdat, struct zone *zone)
+{
+ unsigned int order;
+
+ /* Alloc on stack as interrupts are disabled for zone walk */
+ struct contig_page_info info;
+
+ seq_printf(m, "Node %4d, zone %8s %19s",
+ pgdat->node_id,
+ zone->name, " ");
+ for (order = 0; order < MAX_ORDER; ++order) {
+ fill_contig_page_info(zone, order, &info);
+ seq_printf(m, "%6d ", unusable_free_index(zone, order, &info));
+ }
+
+ seq_putc(m, '\n');
+}
+
+/*
+ * Display unusable free space index
+ * XXX: Could be a lot more efficient, but it's not a critical path
+ */
+static int pagetypeinfo_showunusable(struct seq_file *m, void *arg)
+{
+ pg_data_t *pgdat = (pg_data_t *)arg;
+
+ seq_printf(m, "\nUnusable free space index at order\n");
+ walk_zones_in_node(m, pgdat, pagetypeinfo_showunusable_print);
+
+ return 0;
+}
+
static void pagetypeinfo_showfree_print(struct seq_file *m,
pg_data_t *pgdat, struct zone *zone)
{
@@ -558,6 +656,7 @@ static int pagetypeinfo_show(struct seq_file *m, void *arg)
seq_printf(m, "Pages per block: %lu\n", pageblock_nr_pages);
seq_putc(m, '\n');
pagetypeinfo_showfree(m, pgdat);
+ pagetypeinfo_showunusable(m, pgdat);
pagetypeinfo_showblockcount(m, pgdat);
return 0;
Mel Gorman
locking an anon_vma. One important difference between page_lock_anon_vma()
and rmap_walk_anon() is that the page_lock_anon_vma() takes the RCU lock
before the lookup so that the anon_vma does not disappear. There does not
appear to be locking in place that prevents the anon_vma disappearing before
the spinlock is taken.
This patch puts a rcu_read_lock() around the anon_vma lookup similar to
what page_lock_anon_vma() does to prevent an accidental use-after-free.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
mm/rmap.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index b468d5f..fb695d3 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1233,9 +1233,10 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
* This needs to be reviewed later: avoiding page_lock_anon_vma()
* is risky, and currently limits the usefulness of rmap_walk().
*/
+ rcu_read_lock();
anon_vma = page_anon_vma(page);
if (!anon_vma)
- return ret;
+ goto out_rcu_unlock;
spin_lock(&anon_vma->lock);
/*
@@ -1256,6 +1257,10 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
out_anon_unlock:
spin_unlock(&anon_vma->lock);
+
+out_rcu_unlock:
+ rcu_read_unlock();
+
return ret;
Mel Gorman
references still manage to trigger on ppc64. The most likely cause is a
use-after-free but it's not clear if it's due to a locking problem or
something ppc64 specific. This patch somewhat works around the problem
by checking the contents of the anon_vma make sense before using it but
it needs reviewing by eyes familiar with the page migration code to try
spot where the real problem lies.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
mm/rmap.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index fb695d3..462ac86 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1237,6 +1237,8 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
anon_vma = page_anon_vma(page);
if (!anon_vma)
goto out_rcu_unlock;
+ if (!anon_vma->head.next)
+ goto out_rcu_unlock;
spin_lock(&anon_vma->lock);
/*
Mel Gorman
value is written to the file, all zones are compacted. The expected user
of such a trigger is a job scheduler that prepares the system before the
target application runs.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
Documentation/sysctl/vm.txt | 11 ++++++++
include/linux/compaction.h | 5 +++
kernel/sysctl.c | 11 ++++++++
mm/compaction.c | 60 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 87 insertions(+), 0 deletions(-)
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index fc5790d..92b5b00 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -19,6 +19,7 @@ files can be found in mm/swap.c.
Currently, these files are in /proc/sys/vm:
- block_dump
+- compact_memory
- dirty_background_bytes
- dirty_background_ratio
- dirty_bytes
@@ -64,6 +65,16 @@ information on block I/O debugging is in Documentation/laptops/laptop-mode.txt.
==============================================================
+compact_memory
+
+Available only when CONFIG_COMPACTION is set. When an arbitrary value
+is written to the file, all zones are compacted such that free memory
+is available in contiguous blocks where possible. This can be important
+for example in the allocation of huge pages although processes will also
+directly compact memory as required.
+
+==============================================================
+
dirty_background_bytes
Contains the amount of dirty memory at which the pdflush background writeback
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 6201371..facaa3d 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -5,4 +5,9 @@
#define COMPACT_INCOMPLETE 0
#define COMPACT_COMPLETE 1
+#ifdef CONFIG_COMPACTION
+extern int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
+#endif /* CONFIG_COMPACTION */
+
#endif /* _LINUX_COMPACTION_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8a68b24..a02c816 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -50,6 +50,7 @@
#include <linux/ftrace.h>
#include <linux/slow-work.h>
#include <linux/perf_event.h>
+#include <linux/compaction.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
@@ -80,6 +81,7 @@ extern int pid_max;
extern int min_free_kbytes;
extern int pid_max_min, pid_max_max;
extern int sysctl_drop_caches;
+extern int sysctl_compact_memory;
extern int percpu_pagelist_fraction;
extern int compat_log;
extern int latencytop_enabled;
@@ -1109,6 +1111,15 @@ static struct ctl_table vm_table[] = {
.mode = 0644,
.proc_handler = drop_caches_sysctl_handler,
},
+#ifdef CONFIG_COMPACTION
+ {
+ .procname = "compact_memory",
+ .data = &sysctl_compact_memory,
+ .maxlen = sizeof(int),
+ .mode = 0200,
+ .proc_handler = sysctl_compaction_handler,
+ },
+#endif /* CONFIG_COMPACTION */
{
.procname = "min_free_kbytes",
.data = &min_free_kbytes,
diff --git a/mm/compaction.c b/mm/compaction.c
index 51ec864..c0b9dc9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -11,6 +11,7 @@
#include <linux/migrate.h>
#include <linux/compaction.h>
#include <linux/mm_inline.h>
+#include <linux/sysctl.h>
#include "internal.h"
/*
@@ -339,3 +340,62 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
return ret;
}
+/* Compact all zones within a node */
+static int compact_node(int nid)
+{
+ int zoneid;
+ pg_data_t *pgdat;
+ struct zone *zone;
+
+ if (nid < 0 || nid > nr_node_ids || !node_online(nid))
+ return -EINVAL;
+ pgdat = NODE_DATA(nid);
+
+ /* Flush pending updates to the LRU lists */
+ lru_add_drain_all();
+
+ for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+ struct compact_control cc;
+
+ zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ cc.nr_freepages = 0;
+ cc.nr_migratepages = 0;
+ cc.zone = zone;
+ INIT_LIST_HEAD(&cc.freepages);
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ compact_zone(zone, &cc);
+
+ VM_BUG_ON(!list_empty(&cc.freepages));
+ VM_BUG_ON(!list_empty(&cc.migratepages));
+ }
+
+ return 0;
+}
+
+/* Compact all nodes in the system */
+static int compact_nodes(void)
+{
+ int nid;
+
+ for_each_online_node(nid)
+ compact_node(nid);
+
+ return COMPACT_COMPLETE;
+}
+
+/* The written value is actually unused, all memory is compacted */
+int sysctl_compact_memory;
+
+/* This is the entry point for compacting all nodes via /proc/sys/vm */
+int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ if (write)
+ return compact_nodes();
+
+ return 0;
+}
Mel Gorman
> On Fri, 12 Feb 2010 12:00:53 GMT, Mel Gorman said:
> > This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> > value is written to the file, all zones are compacted. The expected user
> > of such a trigger is a job scheduler that prepares the system before the
> > target application runs.
>
> get by with just one or the other? Should the /proc one live in /sys too?
>
The sysfs trigger is only visible on NUMA. The proc one is easier to use
when the requirement is "compact all memory". There doesn't appear to be a
suitable place in sysfs for the proc trigger as it's already the case that
all proc tunables are not reflected in sysfs.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Valdis.K...@vt.edu
> value is written to the file, all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
Argh. A global trigger in /proc, and a per-node trigger in /sys too. Can we
KOSAKI Motohiro
> takes the allocation size into account. For the most part, the huge page
> size will be the size of interest but not necessarily so it is exported
> on a per-order and per-zone basis via /proc/pagetypeinfo.
Hmmm..
/proc/pagetype have a machine unfriendly format. perhaps, some user have own ugly
/proc/pagetype parser. It have a little risk to break userland ABI.
I have dumb question. Why can't we use another file?
> The index is normally calculated as a value between 0 and 1 which is
> obviously unsuitable within the kernel. Instead, the first three decimal
> places are used as a value between 0 and 1000 for an integer approximation.
I think we can treat separately internal representaion and /proc displaing
style. example, load-average have fixed point internal representaion. but
/proc/loadavg hide it.
So, I personally like to keep this internal representation and change external
representaion to 0.000-1.000 or 0.0%-100.0% range.
I leraned math by japanese. probably then I couldn't understand what mean
"3 decimal places" awhile.
Simply can't we write "Index should be a value between 0 and 1000"?
Mel Gorman
> > Unusuable free space index is a measure of external fragmentation that
> > takes the allocation size into account. For the most part, the huge page
> > size will be the size of interest but not necessarily so it is exported
> > on a per-order and per-zone basis via /proc/pagetypeinfo.
>
> Hmmm..
> /proc/pagetype have a machine unfriendly format. perhaps, some user have own ugly
> /proc/pagetype parser. It have a little risk to break userland ABI.
>
It's very low risk. I doubt there are machine parsers of
/proc/pagetypeinfo because there are very few machine-orientated actions
that can be taken based on the information. It's more informational for
a user if they were investigating fragmentation problems.
> I have dumb question. Why can't we use another file?
>
I could. What do you suggest?
>
> > The index is normally calculated as a value between 0 and 1 which is
> > obviously unsuitable within the kernel. Instead, the first three decimal
> > places are used as a value between 0 and 1000 for an integer approximation.
>
> I think we can treat separately internal representaion and /proc displaing
> style. example, load-average have fixed point internal representaion. but
> /proc/loadavg hide it.
>
> So, I personally like to keep this internal representation and change external
> representaion to 0.000-1.000 or 0.0%-100.0% range.
>
I don't want to use a percentage for this value as there are two
indices, one of which can be expressed as a percentage and the other
not. I can represent it has a value between 0 and 1 if you prefer.
I can do either that or make it really display between 0 and 1. I'd
prefer displaying between 0 and 1 myself.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
KOSAKI Motohiro
> relocating movable pages towards the end of the zone.
>
> A single compaction run involves a migration scanner and a free scanner.
> Both scanners operate on pageblock-sized areas in the zone. The migration
> scanner starts at the bottom of the zone and searches for all movable pages
> within each area, isolating them onto a private list called migratelist.
> The free scanner starts at the top of the zone and searches for suitable
> areas and consumes the free pages within making them available for the
> migration scanner. The pages isolated for migration are then migrated to
> the newly isolated free pages.
>
Dumb question. This patch makes only in-zone comaction. why can't we support
inter zone compaction? usually DMA zone is rare resource rather than NORMAL
zone.
if my remember is correct, now is 2010 :)
pageblock_nr_pages seems too long spin lock holding. why can't we
release spinlock more frequently?
plus, we need prevent too many concurrent compaction. otherwise too
many isolation makes strange oom killer.
> + struct page *page;
> + if (!pfn_valid_within(low_pfn))
> + continue;
> +
> + /* Get the page and skip if free */
> + page = pfn_to_page(low_pfn);
> + if (PageBuddy(page)) {
> + low_pfn += (1 << page_order(page)) - 1;
> + continue;
> + }
> +
> + if (!PageLRU(page) || PageUnevictable(page))
> + continue;
> +
> + /* Try isolate the page */
> + lru_src = page_lru(page);
> + switch (__isolate_lru_page(page, ISOLATE_BOTH, 0)) {
I don't think __isolate_lru_page() is suitable. because it can't isolate
unevictable pages. unevictable pages mean it's undroppable but it can be
migrated.
This is significantly difference between lumpy reclaim and migrate based
compaction. please consider it.
plus, can you please change NR_ISOLATED_FILE/ANON stat in this place. it
help to prevent strange oom issue.
> + case 0:
> + list_move(&page->lru, migratelist);
> + mem_cgroup_del_lru(page);
> + cc->nr_migratepages++;
> + break;
> +
> + case -EBUSY:
> + /*
> + * else it is being freed elsewhere. The
> + * problem is that we are not really sure where
> + * it came from in the first place
> + * XXX: Verify the putback logic is ok. This was
> + * all written before LRU lists were split
> + */
> + list_move(&page->lru, &zone->lru[lru_src].list);
> + mem_cgroup_rotate_lru_list(page, page_lru(page));
> + continue;
we don't need this rotation. probaby you copied it from isolate_lru_pages().
then, I'd like to explain why isolate_lru_pages() need such rotation.
isolate_lru_pages() isolate page by lru order, then if it put back the page
to lru front, next isolate_lru_pages() found the same page. it's obviously
cpu wasting. then we put back the page to lru tail.
but this function isolate pages by pfn order, we don't need such trick imho.
KOSAKI Motohiro
> > > Unusuable free space index is a measure of external fragmentation that
> > > takes the allocation size into account. For the most part, the huge page
> > > size will be the size of interest but not necessarily so it is exported
> > > on a per-order and per-zone basis via /proc/pagetypeinfo.
> >
> > Hmmm..
> > /proc/pagetype have a machine unfriendly format. perhaps, some user have own ugly
> > /proc/pagetype parser. It have a little risk to break userland ABI.
> >
>
> It's very low risk. I doubt there are machine parsers of
> /proc/pagetypeinfo because there are very few machine-orientated actions
> that can be taken based on the information. It's more informational for
> a user if they were investigating fragmentation problems.
>
> > I have dumb question. Why can't we use another file?
>
> I could. What do you suggest?
I agree it's low risk. but personally I hope fragmentation ABI keep very stable because
I expect some person makes userland compaction daemon. (read fragmentation index
from /proc and write /proc/compact_memory if necessary).
then, if possible, I hope fragmentation info have individual /proc file.
Mel Gorman
> > This patch is the core of a mechanism which compacts memory in a zone by
> > relocating movable pages towards the end of the zone.
> >
> > A single compaction run involves a migration scanner and a free scanner.
> > Both scanners operate on pageblock-sized areas in the zone. The migration
> > scanner starts at the bottom of the zone and searches for all movable pages
> > within each area, isolating them onto a private list called migratelist.
> > The free scanner starts at the top of the zone and searches for suitable
> > areas and consumes the free pages within making them available for the
> > migration scanner. The pages isolated for migration are then migrated to
> > the newly isolated free pages.
> >
>
> Dumb question. This patch makes only in-zone comaction. why can't we support
> inter zone compaction? usually DMA zone is rare resource rather than NORMAL
> zone.
>
Because how do I tell in advance that the data I am migrating from DMA can
be safely relocated to the NORMAL zone? We don't save GFP flags. Granted,
for DMA, that will not matter as pages that must be in DMA will also not by
migratable. However, buffer pages should not get relocated to HIGHMEM for
example which is more likely to happen. It could be special cased but
I'm not aware of ZONE_DMA-related pressure problems that would make this
worthwhile and if so, it should be handled as a separate patch series.
Ah, it was 2009 when I last kicked this around heavily :) I'll update
it.
I'll look into isolating in smaller groupings of pages.
>
> > + struct page *page;
> > + if (!pfn_valid_within(low_pfn))
> > + continue;
> > +
> > + /* Get the page and skip if free */
> > + page = pfn_to_page(low_pfn);
> > + if (PageBuddy(page)) {
> > + low_pfn += (1 << page_order(page)) - 1;
> > + continue;
> > + }
> > +
> > + if (!PageLRU(page) || PageUnevictable(page))
> > + continue;
> > +
> > + /* Try isolate the page */
> > + lru_src = page_lru(page);
> > + switch (__isolate_lru_page(page, ISOLATE_BOTH, 0)) {
>
> I don't think __isolate_lru_page() is suitable. because it can't isolate
> unevictable pages. unevictable pages mean it's undroppable but it can be
> migrated.
>
At the moment, I'm not handling unevictable pages at all. This is a very
heavy patchset as it is and would prefer to handle unevictable as a
follow-on patch if possible.
> This is significantly difference between lumpy reclaim and migrate based
> compaction. please consider it.
>
> plus, can you please change NR_ISOLATED_FILE/ANON stat in this place. it
> help to prevent strange oom issue.
>
Is this the significant difference you mean? If so, yes, I can look into
that and what is needed to prevent concurrent compactors.
As it is, the fact that there is a check of fragmentation index
beforehand and of watermarks should prevent too many concurrent
compactors as it would be determined in advance that compaction would
fail. However, it could still collide with lumpy reclaim so they should
be brought more in line.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Mel Gorman
> > On Tue, Feb 16, 2010 at 04:03:29PM +0900, KOSAKI Motohiro wrote:
> > > > Unusuable free space index is a measure of external fragmentation that
> > > > takes the allocation size into account. For the most part, the huge page
> > > > size will be the size of interest but not necessarily so it is exported
> > > > on a per-order and per-zone basis via /proc/pagetypeinfo.
> > >
> > > Hmmm..
> > > /proc/pagetype have a machine unfriendly format. perhaps, some user have own ugly
> > > /proc/pagetype parser. It have a little risk to break userland ABI.
> > >
> >
> > It's very low risk. I doubt there are machine parsers of
> > /proc/pagetypeinfo because there are very few machine-orientated actions
> > that can be taken based on the information. It's more informational for
> > a user if they were investigating fragmentation problems.
> >
> > > I have dumb question. Why can't we use another file?
> >
> > I could. What do you suggest?
>
> I agree it's low risk. but personally I hope fragmentation ABI keep very stable because
> I expect some person makes userland compaction daemon. (read fragmentation index
> from /proc and write /proc/compact_memory if necessary).
> then, if possible, I hope fragmentation info have individual /proc file.
>
I'd be somewhat surprised if there was an active userland compaction daemon
because I'd expect them to be depending on direct compaction. Userspace
compaction is more likely to be an all-or-nothing affair and confined to
NUMA nodes if they are being used as containers. If a compaction daemon was
to exist, I'd have expected it to be in-kernel because the triggers from
userspace are so coarse.
Still, I can break out the indices into separate files to cover all the
bases.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Christoph Lameter
> Because how do I tell in advance that the data I am migrating from DMA can
> be safely relocated to the NORMAL zone? We don't save GFP flags. Granted,
> for DMA, that will not matter as pages that must be in DMA will also not by
> migratable. However, buffer pages should not get relocated to HIGHMEM for
> example which is more likely to happen. It could be special cased but
> I'm not aware of ZONE_DMA-related pressure problems that would make this
> worthwhile and if so, it should be handled as a separate patch series.
Oh there are numerous ZONE_DMA pressure issues if you have ancient /
screwed up hardware that can only operate on DMA or DMA32 memory.
Moving page cache pages out of the DMA zone would be good. A
write request will cause the page to bounce back to the DMA zone if the
device requires the page there.
But I also think that the patchset should be as simple as possible so that
it can be merged soon.
> Ah, it was 2009 when I last kicked this around heavily :) I'll update
> it.
But it was authored in 2009. May be important if patent or other
copyright claims arise. 2009-2010?
Mel Gorman
> On Tue, 16 Feb 2010, Mel Gorman wrote:
>
> > Because how do I tell in advance that the data I am migrating from DMA can
> > be safely relocated to the NORMAL zone? We don't save GFP flags. Granted,
> > for DMA, that will not matter as pages that must be in DMA will also not by
> > migratable. However, buffer pages should not get relocated to HIGHMEM for
> > example which is more likely to happen. It could be special cased but
> > I'm not aware of ZONE_DMA-related pressure problems that would make this
> > worthwhile and if so, it should be handled as a separate patch series.
>
> Oh there are numerous ZONE_DMA pressure issues if you have ancient /
> screwed up hardware that can only operate on DMA or DMA32 memory.
>
I've never ran into the issue. I was under the impression that the only
device that might care these days are floopy disks.
> Moving page cache pages out of the DMA zone would be good. A
> write request will cause the page to bounce back to the DMA zone if the
> device requires the page there.
>
> But I also think that the patchset should be as simple as possible so that
> it can be merged soon.
>
Agreed.
> > Ah, it was 2009 when I last kicked this around heavily :) I'll update
> > it.
>
> But it was authored in 2009. May be important if patent or other
> copyright claims arise. 2009-2010?
>
2007-2010 in that case because 2007 was when I first prototyped this.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Rik van Riel
> CONFIG_MIGRATION currently depends on CONFIG_NUMA or on the architecture
> being able to hot-remove memory. The main users of page migration such as
> sys_move_pages(), sys_migrate_pages() and cpuset process migration are
> only beneficial on NUMA so it makes sense.
>
> As memory compaction will operate within a zone and is useful on both NUMA
> and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the
> user selects CONFIG_COMPACTION as an option.
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
> Reviewed-by: Christoph Lameter<c...@linux-foundation.org>
Reviewed-by: Rik van Riel <ri...@redhat.com>
--
All rights reversed.
Rik van Riel
> takes the allocation size into account. For the most part, the huge page
> size will be the size of interest but not necessarily so it is exported
> on a per-order and per-zone basis via /proc/pagetypeinfo.
>
> The index is normally calculated as a value between 0 and 1 which is
> obviously unsuitable within the kernel. Instead, the first three decimal
> places are used as a value between 0 and 1000 for an integer approximation.
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
--
All rights reversed.
Mel Gorman
> > <SNIP>
I changed it to only isolate in quantities of SWAP_CLUSTER_MAX.
> plus, we need prevent too many concurrent compaction. otherwise too
> many isolation makes strange oom killer.
>
I think the fact that watermarks are checked should prevent this and
processes enter direct reclaim where too_many_isolated() is checked.
>
> > + struct page *page;
> > + if (!pfn_valid_within(low_pfn))
> > + continue;
> > +
> > + /* Get the page and skip if free */
> > + page = pfn_to_page(low_pfn);
> > + if (PageBuddy(page)) {
> > + low_pfn += (1 << page_order(page)) - 1;
> > + continue;
> > + }
> > +
> > + if (!PageLRU(page) || PageUnevictable(page))
> > + continue;
> > +
> > + /* Try isolate the page */
> > + lru_src = page_lru(page);
> > + switch (__isolate_lru_page(page, ISOLATE_BOTH, 0)) {
>
> I don't think __isolate_lru_page() is suitable. because it can't isolate
> unevictable pages. unevictable pages mean it's undroppable but it can be
> migrated.
>
> This is significantly difference between lumpy reclaim and migrate based
> compaction. please consider it.
>
As unevictable pages are being ignored for the moment, I kept with
__isolate_lru_page. Unevictable pages will be a follow-on patch if we
end up agreeing on this set.
> plus, can you please change NR_ISOLATED_FILE/ANON stat in this place. it
> help to prevent strange oom issue.
>
Good point. Also, I was breaking counters for the LRU lists so thanks
for pushing me to look closer at that.
>
> > + case 0:
> > + list_move(&page->lru, migratelist);
> > + mem_cgroup_del_lru(page);
> > + cc->nr_migratepages++;
> > + break;
> > +
> > + case -EBUSY:
> > + /*
> > + * else it is being freed elsewhere. The
> > + * problem is that we are not really sure where
> > + * it came from in the first place
> > + * XXX: Verify the putback logic is ok. This was
> > + * all written before LRU lists were split
> > + */
> > + list_move(&page->lru, &zone->lru[lru_src].list);
> > + mem_cgroup_rotate_lru_list(page, page_lru(page));
> > + continue;
>
> we don't need this rotation. probaby you copied it from isolate_lru_pages().
It was copied, yes.
> then, I'd like to explain why isolate_lru_pages() need such rotation.
> isolate_lru_pages() isolate page by lru order, then if it put back the page
> to lru front, next isolate_lru_pages() found the same page. it's obviously
> cpu wasting. then we put back the page to lru tail.
>
> but this function isolate pages by pfn order, we don't need such trick imho.
>
Good point. I've addressed this in the patch below. Does it address your
concerns?
==== CUT HERE ====
Fix concerns from Kosaki Motohiro (merge with compaction core)
o Fewer pages are isolated. Hence, cc->migrate_pfn in
isolate_migratepages() is updated slightly differently and the debug
checks change
o LRU lists are no longer rotated
o NR_ISOLATED_* is updated
o del_page_from_lru_list() is used instead list_move when isolated so
that the counters get updated correctly.
o Pages that fail to migrate are put back on the LRU promptly to avoid
being isolated for too long.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
include/linux/swap.h | 1 +
mm/compaction.c | 81 +++++++++++++++++++++++++++----------------------
2 files changed, 46 insertions(+), 36 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7e7181b..12566ed 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -151,6 +151,7 @@ enum {
};
#define SWAP_CLUSTER_MAX 32
+#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
#define SWAP_MAP_MAX 0x3e /* Max duplication count, in first swap_map */
#define SWAP_MAP_BAD 0x3f /* Note pageblock is bad, in first swap_map */
diff --git a/mm/compaction.c b/mm/compaction.c
index 11934b3..9d6fd9f 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -27,6 +27,10 @@ struct compact_control {
unsigned long nr_migratepages; /* Number of pages to migrate */
unsigned long free_pfn; /* isolate_freepages search base */
unsigned long migrate_pfn; /* isolate_migratepages search base */
+ /* Account for isolated anon and file pages */
+ unsigned long nr_anon;
+ unsigned long nr_file;
+
struct zone *zone;
};
@@ -155,6 +159,23 @@ static void isolate_freepages(struct zone *zone,
cc->nr_freepages = nr_freepages;
}
+/* Update the number of anon and file isolated pages in the zone) */
+void update_zone_isolated(struct zone *zone, struct compact_control *cc)
+{
+ struct page *page;
+ unsigned int count[NR_LRU_LISTS] = { 0, };
+
+ list_for_each_entry(page, &cc->migratepages, lru) {
+ int lru = page_lru_base_type(page);
+ count[lru]++;
+ }
+
+ cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
+ cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon);
+ __mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file);
+}
+
/*
* Isolate all pages that can be migrated from the block pointed to by
* the migrate scanner within compact_control.
@@ -164,9 +185,8 @@ static unsigned long isolate_migratepages(struct zone *zone,
{
unsigned long low_pfn, end_pfn;
struct list_head *migratelist;
- enum lru_list lru_src;
- low_pfn = ALIGN(cc->migrate_pfn, pageblock_nr_pages);
+ low_pfn = cc->migrate_pfn;
migratelist = &cc->migratepages;
/* Do not scan outside zone boundaries */
@@ -175,11 +195,12 @@ static unsigned long isolate_migratepages(struct zone *zone,
/* Setup to scan one block but not past where we are migrating to */
end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
- cc->migrate_pfn = end_pfn;
- VM_BUG_ON(end_pfn > cc->free_pfn);
- if (!pfn_valid(low_pfn))
+ /* Do not cross the free scanner or scan within a memory hole */
+ if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
+ cc->migrate_pfn = end_pfn;
return 0;
+ }
migrate_prep();
@@ -201,31 +222,22 @@ static unsigned long isolate_migratepages(struct zone *zone,
continue;
/* Try isolate the page */
- lru_src = page_lru(page);
- switch (__isolate_lru_page(page, ISOLATE_BOTH, 0)) {
- case 0:
- list_move(&page->lru, migratelist);
+ if (__isolate_lru_page(page, ISOLATE_BOTH, 0) == 0) {
+ del_page_from_lru_list(zone, page, page_lru(page));
+ list_add(&page->lru, migratelist);
mem_cgroup_del_lru(page);
cc->nr_migratepages++;
+ }
+
+ /* Avoid isolating too much */
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
break;
+ }
- case -EBUSY:
- /*
- * else it is being freed elsewhere. The
- * problem is that we are not really sure where
- * it came from in the first place
- * XXX: Verify the putback logic is ok. This was
- * all written before LRU lists were split
- */
- list_move(&page->lru, &zone->lru[lru_src].list);
- mem_cgroup_rotate_lru_list(page, page_lru(page));
- continue;
+ update_zone_isolated(zone, cc);
- default:
- BUG();
- }
- }
spin_unlock_irq(&zone->lru_lock);
+ cc->migrate_pfn = low_pfn;
return cc->nr_migratepages;
}
@@ -318,24 +330,21 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
if (nr_remaining)
count_vm_events(COMPACTPAGEFAILED, nr_remaining);
+
+ /* Release LRU pages not migrated */
+ if (!list_empty(&cc->migratepages)) {
+ putback_lru_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ }
+
+ mod_zone_page_state(zone, NR_ISOLATED_ANON, -cc->nr_anon);
+ mod_zone_page_state(zone, NR_ISOLATED_FILE, -cc->nr_file);
}
/* Release free pages and check accounting */
cc->nr_freepages -= release_freepages(zone, &cc->freepages);
VM_BUG_ON(cc->nr_freepages != 0);
- /*
- * Release LRU pages not migrated
- * XXX: Page migration at this point tries fairly hard to move
- * pages as it is but if migration fails, pages are left
- * on cc->migratepages for more passes. This might cause
- * multiple useless failures. Watch compact_pagemigrate_failed
- * in /proc/vmstat. If it grows a lot, then putback should
- * happen after each failed migration
- */
- if (!list_empty(&cc->migratepages))
- putback_lru_pages(&cc->migratepages);
-
return ret;
Rik van Riel
> Fix concerns from Kosaki Motohiro (merge with compaction core)
>
> o Fewer pages are isolated. Hence, cc->migrate_pfn in
> isolate_migratepages() is updated slightly differently and the debug
> checks change
> o LRU lists are no longer rotated
> o NR_ISOLATED_* is updated
> o del_page_from_lru_list() is used instead list_move when isolated so
> that the counters get updated correctly.
> o Pages that fail to migrate are put back on the LRU promptly to avoid
> being isolated for too long.
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
Consider this an ack to your patch 5/12 with these fixes.
--
All rights reversed.
Rik van Riel
> value is written to the file, all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
--
All rights reversed.
Rik van Riel
> written to, each zone in that node is compacted. The intention that this
> would be used by something like a job scheduler in a batch system before
> a job starts so that the job can allocate the maximum number of
> hugepages without significant start-up cost.
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
--
All rights reversed.
Mel Gorman
> There appears to be a race in rmap_walk_anon() that can be triggered by using
> page migration under heavy load on pages that do not belong to the process
> doing the migration - e.g. during memory compaction. The bug triggered is
> a NULL pointer deference in list_for_each_entry().
>
Incidentally, I hate patches 10-12 with the last one in particular being
outright flaky. I'm looking at copying the KSM approach instead and have
started tests using the following patch. Any comments on this approach
for ensuring the anon_vma exists for as long as it's needed? Obviously,
the refcounts for KSM and migrate can be collapsed to save space but this
is clearer to review.
=== CUT HERE ====
mm,migration: Take a reference to the anon_vma before migrating
rmap_walk_anon() does not use page_lock_anon_vma() for looking up and
locking an anon_vma and it does not appear to have sufficient locking to
ensure the anon_vma does not disappear from under it.
This patch copies an approach used by KSM to take a reference on the
anon_vma while pages are being migrated. This should prevent rmap_walk()
running into nasty surprises later because anon_vma has been freed.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
include/linux/rmap.h | 23 +++++++++++++++++++++++
mm/migrate.c | 12 ++++++++++++
mm/rmap.c | 10 +++++-----
3 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b019ae6..6b5a1a9 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -29,6 +29,9 @@ struct anon_vma {
#ifdef CONFIG_KSM
atomic_t ksm_refcount;
#endif
+#ifdef CONFIG_MIGRATION
+ atomic_t migrate_refcount;
+#endif
/*
* NOTE: the LSB of the head.next is set by
* mm_take_all_locks() _after_ taking the above lock. So the
@@ -61,6 +64,26 @@ static inline int ksm_refcount(struct anon_vma *anon_vma)
return 0;
}
#endif /* CONFIG_KSM */
+#ifdef CONFIG_MIGRATION
+static inline void migrate_refcount_init(struct anon_vma *anon_vma)
+{
+ atomic_set(&anon_vma->migrate_refcount, 0);
+}
+
+static inline int migrate_refcount(struct anon_vma *anon_vma)
+{
+ return atomic_read(&anon_vma->migrate_refcount);
+}
+#else
+static inline void migrate_refcount_init(struct anon_vma *anon_vma)
+{
+}
+
+static inline int migrate_refcount(struct anon_vma *anon_vma)
+{
+ return 0;
+}
+#endif /* CONFIG_MIGRATE */
static inline struct anon_vma *page_anon_vma(struct page *page)
{
diff --git a/mm/migrate.c b/mm/migrate.c
index 9a0db5b..63addfa 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -551,6 +551,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
int rcu_locked = 0;
int charge = 0;
struct mem_cgroup *mem = NULL;
+ struct anon_vma *anon_vma = NULL;
if (!newpage)
return -ENOMEM;
@@ -607,6 +608,8 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (PageAnon(page)) {
rcu_read_lock();
rcu_locked = 1;
+ anon_vma = page_anon_vma(page);
+ atomic_inc(&anon_vma->migrate_refcount);
}
/*
@@ -646,6 +649,15 @@ skip_unmap:
if (rc)
remove_migration_ptes(page, page);
rcu_unlock:
+
+ /* Drop an anon_vma reference if we took one */
+ if (anon_vma && atomic_dec_and_lock(&anon_vma->migrate_refcount, &anon_vma->lock)) {
+ int empty = list_empty(&anon_vma->head);
+ spin_unlock(&anon_vma->lock);
+ if (empty)
+ anon_vma_free(anon_vma);
+ }
+
if (rcu_locked)
rcu_read_unlock();
uncharge:
diff --git a/mm/rmap.c b/mm/rmap.c
index 278cd27..11ba74a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -172,7 +172,8 @@ void anon_vma_unlink(struct vm_area_struct *vma)
list_del(&vma->anon_vma_node);
/* We must garbage collect the anon_vma if it's empty */
- empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma);
+ empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma) &&
+ !migrate_refcount(anon_vma);
spin_unlock(&anon_vma->lock);
if (empty)
@@ -185,6 +186,7 @@ static void anon_vma_ctor(void *data)
spin_lock_init(&anon_vma->lock);
ksm_refcount_init(anon_vma);
+ migrate_refcount_init(anon_vma);
INIT_LIST_HEAD(&anon_vma->head);
}
@@ -1228,10 +1230,8 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
/*
* Note: remove_migration_ptes() cannot use page_lock_anon_vma()
* because that depends on page_mapped(); but not all its usages
- * are holding mmap_sem, which also gave the necessary guarantee
- * (that this anon_vma's slab has not already been destroyed).
- * This needs to be reviewed later: avoiding page_lock_anon_vma()
- * is risky, and currently limits the usefulness of rmap_walk().
+ * are holding mmap_sem. Users without mmap_sem are required to
+ * take a reference count to prevent the anon_vma disappearing
*/
anon_vma = page_anon_vma(page);
if (!anon_vma)
Rik van Riel
> fragmentation, a compaction run complete and an allocation failure still
> fail. There are two obvious reasons as to why
>
> o Page migration cannot move all pages so fragmentation remains
> o A suitable page may exist but watermarks are not met
>
> In the event of compaction and allocation failure, this patch prevents
> compaction happening for a short interval. It's only recorded on the
> preferred zone but that should be enough coverage. This could have been
> implemented similar to the zonelist_cache but the increased size of the
> zonelist did not appear to be justified.
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
--
All rights reversed.
Minchan Kim
> Unusuable free space index is a measure of external fragmentation that
> takes the allocation size into account. For the most part, the huge page
> size will be the size of interest but not necessarily so it is exported
> on a per-order and per-zone basis via /proc/pagetypeinfo.
>
> The index is normally calculated as a value between 0 and 1 which is
> obviously unsuitable within the kernel. Instead, the first three decimal
> places are used as a value between 0 and 1000 for an integer approximation.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
There are comments at below.
It's very trivial so I don't care.
Did you remain "zone" argument for later?
Anyway, It's trivial.
> + unsigned int order,
> + struct contig_page_info *info)
> +{
> + /* No free memory is interpreted as all free memory is unusable */
> + if (info->free_pages == 0)
> + return 1000;
> +
> + /*
> + * Index should be a value between 0 and 1. Return a value to 3
> + * decimal places.
> + *
> + * 0 => no fragmentation
> + * 1 => high fragmentation
> + */
> + return ((info->free_pages - (info->free_blocks_suitable << order)) * 1000) / info->free_pages;
> +
> +}
> +
> +static void pagetypeinfo_showunusable_print(struct seq_file *m,
> + pg_data_t *pgdat, struct zone *zone)
> +{
> + unsigned int order;
> +
> + /* Alloc on stack as interrupts are disabled for zone walk */
contig_page_info would be larger than now?
I think it's small data now. I don't know why you comment it.
It's just out of curiosity. :)
--
Kind regards,
Minchan Kim
Mel Gorman
> On Fri, 2010-02-12 at 12:00 +0000, Mel Gorman wrote:
> > Unusuable free space index is a measure of external fragmentation that
> > takes the allocation size into account. For the most part, the huge page
> > size will be the size of interest but not necessarily so it is exported
> > on a per-order and per-zone basis via /proc/pagetypeinfo.
> >
> > The index is normally calculated as a value between 0 and 1 which is
> > obviously unsuitable within the kernel. Instead, the first three decimal
> > places are used as a value between 0 and 1000 for an integer approximation.
> >
> > Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> Reviewed-by: Minchan Kim <minch...@gmail.com>
>
> There are comments at below.
> It's very trivial so I don't care.
>
Thanks
It's an oversight. I'll remove the parameter as unnecessary. It was
needed in an earlier iteration.
It is small data. I don't remember why I felt the need to spell out why
I didn't use kmalloc(). I'll drop the comment as it's not very helpful.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Minchan Kim
"zone" argument.
> +{
> + struct page *page, *next;
> + int count = 0;
> +
> + list_for_each_entry_safe(page, next, freelist, lru) {
> + list_del(&page->lru);
> + __free_page(page);
> + count++;
> + }
> +
> + return count;
> +}
> +
> +/* Isolate free pages onto a private freelist. Must hold zone->lock */
> +static int isolate_freepages_block(struct zone *zone,
return type 'int'?
I think we can't return signed value.
We are progressing backward by physical page order in a zone.
If we meet crossover between zone, Why are we going backward
continuously? Before it happens, migration and free scanner would meet.
Am I miss something?
> +
> + /* Check the block is suitable for migration */
> + if (!suitable_migration_target(page))
> + continue;
Dumb question.
suitable_migration_target considers three type's pages
1. free page and page's order >= pageblock_order
2. free pages and pages's order < pageblock_order with movable page
3. used page with movable
I can understand 1 and 2 but can't 3. This function is for gathering
free page. How do you handle used page as free one?
In addition, as I looked into isolate_freepages_block, it doesn't
consider 3 by PageBuddy check.
I am confusing. Pz, correct me.
Sometime, this function changes pages's type to MIGRATE_MOVABLE.
I hope adding comment about that.
--
Kind regards,
Minchan Kim
Mel Gorman
I removed it. Thanks
> > +{
> > + struct page *page, *next;
> > + int count = 0;
> > +
> > + list_for_each_entry_safe(page, next, freelist, lru) {
> > + list_del(&page->lru);
> > + __free_page(page);
> > + count++;
> > + }
> > +
> > + return count;
> > +}
> > +
> > +/* Isolate free pages onto a private freelist. Must hold zone->lock */
> > +static int isolate_freepages_block(struct zone *zone,
>
> return type 'int'?
> I think we can't return signed value.
>
I don't understand your query. What's wrong with returning int?
Incidentally, this line is wrong but will be fixed in line 3. If
split_free_page() fails, it causes an infinite loop.
I was considering a situation like the following
Node-0 Node-1 Node-0
DMA DMA DMA
0-1023 1024-2047 2048-4096
In that case, a PFN scanner can enter a new node and zone but the migrate
and free scanners have not necessarily met. This configuration is *extremely*
rare but it happens on messed-up LPAR configurations on POWER.
> > +
> > + /* Check the block is suitable for migration */
> > + if (!suitable_migration_target(page))
> > + continue;
>
> Dumb question.
> suitable_migration_target considers three type's pages
>
> 1. free page and page's order >= pageblock_order
> 2. free pages and pages's order < pageblock_order with movable page
> 3. used page with movable
>
> I can understand 1 and 2 but can't 3. This function is for gathering
> free page. How do you handle used page as free one?
>
> In addition, as I looked into isolate_freepages_block, it doesn't
> consider 3 by PageBuddy check.
>
> I am confusing. Pz, correct me.
>
I'm afraid I don't understand your question. At the point
suitable_migration_target() is called, the only concern is finding a pageblock
of pages that should be scanned for free pages by isolate_freepages_block().
What do you mean by "used page with movable" ?
There is a comment within the function about it. Do you want it moved to
here?
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Mel Gorman
takes the allocation size into account. For the most part, the huge page
size will be the size of interest but not necessarily so it is exported
The index is a value between 0 and 1. It can be expressed as a
percentage by multiplying by 100 as documented in
Documentation/filesystems/proc.txt.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
Documentation/filesystems/proc.txt | 13 ++++-
mm/vmstat.c | 120 ++++++++++++++++++++++++++++++++++++
2 files changed, 132 insertions(+), 1 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 1829dfb..57869d0 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -443,6 +443,7 @@ Table 1-5: Kernel info in /proc
sys See chapter 2
sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
tty Info of tty drivers
+ unusable_index Additional page allocator information (see text)(2.5)
uptime System uptime
version Kernel version
video bttv info of video resources (2.4)
@@ -596,7 +597,7 @@ ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...
More information relevant to external fragmentation can be found in
-pagetypeinfo.
+pagetypeinfo and unusable_index
> cat /proc/pagetypeinfo
Page block order: 9
@@ -637,6 +638,16 @@ unless memory has been mlock()'d. Some of the Reclaimable blocks should
also be allocatable although a lot of filesystem metadata may have to be
reclaimed to achieve this.
+> cat /proc/unusable_index
+Node 0, zone DMA 0.000 0.000 0.000 0.001 0.005 0.013 0.021 0.037 0.037 0.101 0.230
+Node 0, zone Normal 0.000 0.000 0.000 0.001 0.002 0.002 0.005 0.015 0.028 0.028 0.054
+
+The unusable free space index measures how much of the available free
+memory cannot be used to satisfy an allocation of a given size and is a
+value between 0 and 1. The higher the value, the more of free memory is
+unusable and by implication, the worse the external fragmentation is. This
+can be expressed as a percentage by multiplying by 100.
+
..............................................................................
meminfo:
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 6051fba..23f217e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -451,6 +451,106 @@ static int frag_show(struct seq_file *m, void *arg)
return 0;
}
+
+struct contig_page_info {
+ unsigned long free_pages;
+ unsigned long free_blocks_total;
+ unsigned long free_blocks_suitable;
+};
+
+/*
+ * Calculate the number of free pages in a zone, how many contiguous
+ * pages are free and how many are large enough to satisfy an allocation of
+ * the target size. Note that this function makes to attempt to estimate
+ * how many suitable free blocks there *might* be if MOVABLE pages were
+ * migrated. Calculating that is possible, but expensive and can be
+ * figured out from userspace
+ */
+static void fill_contig_page_info(struct zone *zone,
+ unsigned int suitable_order,
+ struct contig_page_info *info)
+{
+ unsigned int order;
+
+ info->free_pages = 0;
+ info->free_blocks_total = 0;
+ info->free_blocks_suitable = 0;
+
+ for (order = 0; order < MAX_ORDER; order++) {
+ unsigned long blocks;
+
+ /* Count number of free blocks */
+ blocks = zone->free_area[order].nr_free;
+ info->free_blocks_total += blocks;
+
+ /* Count free base pages */
+ info->free_pages += blocks << order;
+
+ /* Count the suitable free blocks */
+ if (order >= suitable_order)
+ info->free_blocks_suitable += blocks <<
+ (order - suitable_order);
+ }
+}
+
+/*
+ * Return an index indicating how much of the available free memory is
+ * unusable for an allocation of the requested size.
+ */
+static int unusable_free_index(unsigned int order,
+ struct contig_page_info *info)
+{
+ /* No free memory is interpreted as all free memory is unusable */
+ if (info->free_pages == 0)
+ return 1000;
+
+ /*
+ * Index should be a value between 0 and 1. Return a value to 3
+ * decimal places.
+ *
+ * 0 => no fragmentation
+ * 1 => high fragmentation
+ */
+ return ((info->free_pages - (info->free_blocks_suitable << order)) * 1000) / info->free_pages;
+
+}
+
+static void unusable_show_print(struct seq_file *m,
+ pg_data_t *pgdat, struct zone *zone)
+{
+ unsigned int order;
+ int index;
+ struct contig_page_info info;
+
+ seq_printf(m, "Node %d, zone %8s ",
+ pgdat->node_id,
+ zone->name);
+ for (order = 0; order < MAX_ORDER; ++order) {
+ fill_contig_page_info(zone, order, &info);
+ index = unusable_free_index(order, &info);
+ seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
+ }
+
+ seq_putc(m, '\n');
+}
+
+/*
+ * Display unusable free space index
+ * XXX: Could be a lot more efficient, but it's not a critical path
+ */
+static int unusable_show(struct seq_file *m, void *arg)
+{
+ pg_data_t *pgdat = (pg_data_t *)arg;
+
+ /* check memoryless node */
+ if (!node_state(pgdat->node_id, N_HIGH_MEMORY))
+ return 0;
+
+ walk_zones_in_node(m, pgdat, unusable_show_print);
+
+ return 0;
+}
+
static void pagetypeinfo_showfree_print(struct seq_file *m,
pg_data_t *pgdat, struct zone *zone)
{
@@ -601,6 +701,25 @@ static const struct file_operations pagetypeinfo_file_ops = {
.release = seq_release,
};
+static const struct seq_operations unusable_op = {
+ .start = frag_start,
+ .next = frag_next,
+ .stop = frag_stop,
+ .show = unusable_show,
+};
+
+static int unusable_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &unusable_op);
+}
+
+static const struct file_operations unusable_file_ops = {
+ .open = unusable_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
#ifdef CONFIG_ZONE_DMA
#define TEXT_FOR_DMA(xx) xx "_dma",
#else
@@ -944,6 +1063,7 @@ static int __init setup_vmstat(void)
#ifdef CONFIG_PROC_FS
proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
proc_create("pagetypeinfo", S_IRUGO, NULL, &pagetypeinfo_file_ops);
+ proc_create("unusable_index", S_IRUGO, NULL, &unusable_file_ops);
proc_create("vmstat", S_IRUGO, NULL, &proc_vmstat_file_operations);
proc_create("zoneinfo", S_IRUGO, NULL, &proc_zoneinfo_file_operations);
#endif
--
1.6.5
Mel Gorman
given size would fail. The index indicates whether an allocation failure is
due to a lack of memory (values towards 0) or due to external fragmentation
(value towards 1). For the most part, the huge page size will be the size
of interest but not necessarily so it is exported on a per-order and per-zone
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
Documentation/filesystems/proc.txt | 14 ++++++-
mm/vmstat.c | 81 ++++++++++++++++++++++++++++++++++++
2 files changed, 94 insertions(+), 1 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 57869d0..24396ab 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -412,6 +412,7 @@ Table 1-5: Kernel info in /proc
filesystems Supported filesystems
driver Various drivers grouped here, currently rtc (2.4)
execdomains Execdomains, related to security (2.4)
+ extfrag_index Additional page allocator information (see text) (2.5)
fb Frame Buffer devices (2.4)
fs File system parameters, currently nfs/exports (2.4)
ide Directory containing info about the IDE subsystem
@@ -597,7 +598,7 @@ ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...
More information relevant to external fragmentation can be found in
-pagetypeinfo and unusable_index
+pagetypeinfo, unusable_index and extfrag_index.
> cat /proc/pagetypeinfo
Page block order: 9
@@ -648,6 +649,17 @@ value between 0 and 1. The higher the value, the more of free memory is
unusable and by implication, the worse the external fragmentation is. This
can be expressed as a percentage by multiplying by 100.
+> cat /proc/extfrag_index
+Node 0, zone DMA -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.00
+Node 0, zone Normal -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 0.954
+
+The external fragmentation index, is only meaningful if an allocation
+would fail and indicates what the failure is due to. A value of -1 such as
+in many of the examples above states that the allocation would succeed.
+If it would fail, the value is between 0 and 1. A value tending towards
+0 implies the allocation failed due to a lack of memory. A value tending
+towards 1 implies it failed due to external fragmentation.
+
..............................................................................
meminfo:
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 23f217e..fa5975c 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -551,6 +551,67 @@ static int unusable_show(struct seq_file *m, void *arg)
return 0;
}
+/*
+ * A fragmentation index only makes sense if an allocation of a requested
+ * size would fail. If that is true, the fragmentation index indicates
+ * whether external fragmentation or a lack of memory was the problem.
+ * The value can be used to determine if page reclaim or compaction
+ * should be used
+ */
+int fragmentation_index(unsigned int order, struct contig_page_info *info)
+{
+ unsigned long requested = 1UL << order;
+
+ if (!info->free_blocks_total)
+ return 0;
+
+ /* Fragmentation index only makes sense when a request would fail */
+ if (info->free_blocks_suitable)
+ return -1000;
+
+ /*
+ * Index is between 0 and 1 so return within 3 decimal places
+ *
+ * 0 => allocation would fail due to lack of memory
+ * 1 => allocation would fail due to fragmentation
+ */
+ return 1000 - ( (1000+(info->free_pages * 1000 / requested)) / info->free_blocks_total);
+}
+
+
+static void extfrag_show_print(struct seq_file *m,
+ pg_data_t *pgdat, struct zone *zone)
+{
+ unsigned int order;
+ int index;
+
+ /* Alloc on stack as interrupts are disabled for zone walk */
+ struct contig_page_info info;
+
+ seq_printf(m, "Node %d, zone %8s ",
+ pgdat->node_id,
+ zone->name);
+ for (order = 0; order < MAX_ORDER; ++order) {
+ fill_contig_page_info(zone, order, &info);
+ index = fragmentation_index(order, &info);
+ seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
+ }
+
+ seq_putc(m, '\n');
+}
+
+/*
+ * Display fragmentation index for orders that allocations would fail for
+ */
+static int extfrag_show(struct seq_file *m, void *arg)
+{
+ pg_data_t *pgdat = (pg_data_t *)arg;
+
+ walk_zones_in_node(m, pgdat, extfrag_show_print);
+
+ return 0;
+}
+
static void pagetypeinfo_showfree_print(struct seq_file *m,
pg_data_t *pgdat, struct zone *zone)
{
@@ -720,6 +781,25 @@ static const struct file_operations unusable_file_ops = {
.release = seq_release,
};
+static const struct seq_operations extfrag_op = {
+ .start = frag_start,
+ .next = frag_next,
+ .stop = frag_stop,
+ .show = extfrag_show,
+};
+
+static int extfrag_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &extfrag_op);
+}
+
+static const struct file_operations extfrag_file_ops = {
+ .open = extfrag_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
#ifdef CONFIG_ZONE_DMA
#define TEXT_FOR_DMA(xx) xx "_dma",
#else
@@ -1064,6 +1144,7 @@ static int __init setup_vmstat(void)
proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
proc_create("pagetypeinfo", S_IRUGO, NULL, &pagetypeinfo_file_ops);
proc_create("unusable_index", S_IRUGO, NULL, &unusable_file_ops);
+ proc_create("extfrag_index", S_IRUGO, NULL, &extfrag_file_ops);
Mel Gorman
value is written to the file, all zones are compacted. The expected user
of such a trigger is a job scheduler that prepares the system before the
target application runs.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
#endif /* _LINUX_COMPACTION_H */
diff --git a/mm/compaction.c b/mm/compaction.c
index 14ba0ac..22f223f 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -11,6 +11,7 @@
#include <linux/migrate.h>
#include <linux/compaction.h>
#include <linux/mm_inline.h>
+#include <linux/sysctl.h>
#include "internal.h"
/*
@@ -345,3 +346,62 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
return ret;
}
+/* Compact all zones within a node */
+static int compact_node(int nid)
+{
+ int zoneid;
+ pg_data_t *pgdat;
+ struct zone *zone;
+
+
+ return 0;
+}
+
+/* Compact all nodes in the system */
+static int compact_nodes(void)
+{
+ int nid;
+
+ for_each_online_node(nid)
+ compact_node(nid);
+
+ return COMPACT_COMPLETE;
+}
+
+/* The written value is actually unused, all memory is compacted */
+int sysctl_compact_memory;
+
+/* This is the entry point for compacting all nodes via /proc/sys/vm */
+int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ if (write)
+ return compact_nodes();
+
+ return 0;
+}
Mel Gorman
fragmentation, a compaction run complete and an allocation failure still
fail. There are two obvious reasons as to why
o Page migration cannot move all pages so fragmentation remains
o A suitable page may exist but watermarks are not met
In the event of compaction and allocation failure, this patch prevents
compaction happening for a short interval. It's only recorded on the
preferred zone but that should be enough coverage. This could have been
implemented similar to the zonelist_cache but the increased size of the
zonelist did not appear to be justified.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
---
include/linux/compaction.h | 35 +++++++++++++++++++++++++++++++++++
include/linux/mmzone.h | 7 +++++++
mm/page_alloc.c | 5 ++++-
3 files changed, 46 insertions(+), 1 deletions(-)
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 1cf95e2..8b1471b 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -13,6 +13,32 @@ extern int sysctl_compaction_handler(struct ctl_table *table, int write,
extern int fragmentation_index(struct zone *zone, unsigned int order);
extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *mask);
+
+/* defer_compaction - Do not compact within a zone until a given time */
+static inline void defer_compaction(struct zone *zone, unsigned long resume)
+{
+ /*
+ * This function is called when compaction fails to result in a page
+ * allocation success. This is somewhat unsatisfactory as the failure
+ * to compact has nothing to do with time and everything to do with
+ * the requested order, the number of free pages and watermarks. How
+ * to wait on that is more unclear, but the answer would apply to
+ * other areas where the VM waits based on time.
+ */
+ zone->compact_resume = resume;
+}
+
+static inline int compaction_deferred(struct zone *zone)
+{
+ /* init once if necessary */
+ if (unlikely(!zone->compact_resume)) {
+ zone->compact_resume = jiffies;
+ return 0;
+ }
+
+ return time_before(jiffies, zone->compact_resume);
+}
+
#else
static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask)
@@ -20,6 +46,15 @@ static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
return COMPACT_INCOMPLETE;
}
+static inline void defer_compaction(struct zone *zone, unsigned long resume)
+{
+}
+
+static inline int compaction_deferred(struct zone *zone)
+{
+ return 1;
+}
+
#endif /* CONFIG_COMPACTION */
#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 30fe668..31fb38b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -328,6 +328,13 @@ struct zone {
unsigned long *pageblock_flags;
#endif /* CONFIG_SPARSEMEM */
+#ifdef CONFIG_COMPACTION
+ /*
+ * If a compaction fails, do not try compaction again until
+ * jiffies is after the value of compact_resume
+ */
+ unsigned long compact_resume;
+#endif
ZONE_PADDING(_pad1_)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1910b8b..7021c68 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1730,7 +1730,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
cond_resched();
/* Try memory compaction for high-order allocations before reclaim */
- if (order) {
+ if (order && !compaction_deferred(preferred_zone)) {
*did_some_progress = try_to_compact_pages(zonelist,
order, gfp_mask, nodemask);
if (*did_some_progress != COMPACT_INCOMPLETE) {
@@ -1750,6 +1750,9 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
*/
count_vm_event(COMPACTFAIL);
+ /* On failure, avoid compaction for a short time. */
+ defer_compaction(preferred_zone, jiffies + HZ/50);
+
cond_resched();
Mel Gorman
locking an anon_vma and it does not appear to have sufficient locking to
ensure the anon_vma does not disappear from under it.
This patch copies an approach used by KSM to take a reference on the
anon_vma while pages are being migrated. This should prevent rmap_walk()
running into nasty surprises later because anon_vma has been freed.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
+}
+
+static inline int migrate_refcount(struct anon_vma *anon_vma)
+{
+ return atomic_read(&anon_vma->migrate_refcount);
+}
+#else
+static inline void migrate_refcount_init(struct anon_vma *anon_vma)
+{
+}
+
+static inline int migrate_refcount(struct anon_vma *anon_vma)
+{
+ return 0;
+}
Mel Gorman
relocating movable pages towards the end of the zone.
A single compaction run involves a migration scanner and a free scanner.
Both scanners operate on pageblock-sized areas in the zone. The migration
scanner starts at the bottom of the zone and searches for all movable pages
within each area, isolating them onto a private list called migratelist.
The free scanner starts at the top of the zone and searches for suitable
areas and consumes the free pages within making them available for the
migration scanner. The pages isolated for migration are then migrated to
the newly isolated free pages.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
---
include/linux/compaction.h | 8 +
include/linux/mm.h | 1 +
include/linux/swap.h | 6 +
include/linux/vmstat.h | 1 +
mm/Makefile | 1 +
mm/compaction.c | 347 ++++++++++++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 37 +++++
mm/vmscan.c | 5 -
mm/vmstat.c | 5 +
9 files changed, 406 insertions(+), 5 deletions(-)
index a2602a8..12566ed 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -151,6 +151,7 @@ enum {
};
#define SWAP_CLUSTER_MAX 32
+#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
#define SWAP_MAP_MAX 0x3e /* Max duplication count, in first swap_map */
#define SWAP_MAP_BAD 0x3f /* Note pageblock is bad, in first swap_map */
@@ -238,6 +239,11 @@ static inline void lru_cache_add_active_file(struct page *page)
__lru_cache_add(page, LRU_ACTIVE_FILE);
}
+/* LRU Isolation modes. */
+#define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
+#define ISOLATE_ACTIVE 1 /* Isolate active pages. */
+#define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
+
/* linux/mm/vmscan.c */
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *mask);
index 0000000..14ba0ac
--- /dev/null
+++ b/mm/compaction.c
@@ -0,0 +1,347 @@
+/*
+ * linux/mm/compaction.c
+ *
+ * Memory compaction for the reduction of external fragmentation. Note that
+ * this heavily depends upon page migration to do all the real heavy
+ * lifting
+ *
+ * Copyright IBM Corp. 2007-2010 Mel Gorman <m...@csn.ul.ie>
+ */
+#include <linux/swap.h>
+#include <linux/migrate.h>
+#include <linux/compaction.h>
+#include <linux/mm_inline.h>
+#include "internal.h"
+
+/*
+ * compact_control is used to track pages being migrated and the free pages
+ * they are being migrated to during memory compaction. The free_pfn starts
+ * at the end of a zone and migrate_pfn begins at the start. Movable pages
+ * are moved to the end of a zone during a compaction run and the run
+ * completes when free_pfn <= migrate_pfn
+ */
+struct compact_control {
+ struct list_head freepages; /* List of free pages to migrate to */
+ struct list_head migratepages; /* List of pages being migrated */
+ unsigned long nr_freepages; /* Number of isolated free pages */
+ unsigned long nr_migratepages; /* Number of pages to migrate */
+ unsigned long free_pfn; /* isolate_freepages search base */
+ unsigned long migrate_pfn; /* isolate_migratepages search base */
+
+ /* Account for isolated anon and file pages */
+ unsigned long nr_anon;
+ unsigned long nr_file;
+
+ struct zone *zone;
+};
+
+static int release_freepages(struct list_head *freelist)
+{
+ struct page *page, *next;
+ int count = 0;
+
+ list_for_each_entry_safe(page, next, freelist, lru) {
+ list_del(&page->lru);
+ __free_page(page);
+ count++;
+ }
+
+ return count;
+}
+
+/* Isolate free pages onto a private freelist. Must hold zone->lock */
+static int isolate_freepages_block(struct zone *zone,
+ /* If a page was split, advance to the end of it */
+ if (isolated)
+ blockpfn += isolated - 1;
+ }
+
+ return total_isolated;
+}
+
+/* Returns 1 if the page is within a block suitable for migration to */
+static int suitable_migration_target(struct page *page)
+{
+ /* If the page is a large free page, then allow migration */
+ if (PageBuddy(page) && page_order(page) >= pageblock_order)
+ return 1;
+
+ /* If the block is MIGRATE_MOVABLE, allow migration */
+ if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)
+ return 1;
+
+ /* Otherwise skip the block */
+ return 0;
+}
+
+/*
+ * Based on information in the current compact_control, find blocks
+ * suitable for isolating free pages from
+ */
+static void isolate_freepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ struct page *page;
+ unsigned long high_pfn, low_pfn, pfn;
+ unsigned long flags;
+ int nr_freepages = cc->nr_freepages;
+ struct list_head *freelist = &cc->freepages;
+
+ pfn = cc->free_pfn;
+ low_pfn = cc->migrate_pfn + pageblock_nr_pages;
+ high_pfn = low_pfn;
+
+ /*
+ * Isolate free pages until enough are available to migrate the
+ * pages on cc->migratepages. We stop searching if the migrate
+ * and free page scanners meet or enough free pages are isolated.
+ */
+ spin_lock_irqsave(&zone->lock, flags);
+ for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
+ pfn -= pageblock_nr_pages) {
+ int isolated;
+
+ if (!pfn_valid(pfn))
+ continue;
+
+ /* Check for overlapping nodes/zones */
+ page = pfn_to_page(pfn);
+ if (page_zone(page) != zone)
+ continue;
+
+ /* Check the block is suitable for migration */
+ if (!suitable_migration_target(page))
+ continue;
+
+ /* Found a block suitable for isolating free pages from */
+ isolated = isolate_freepages_block(zone, pfn, freelist);
+ nr_freepages += isolated;
+
+ /*
+ * Record the highest PFN we isolated pages from. When next
+ * looking for free pages, the search will restart here as
+ * page migration may have returned some pages to the allocator
+ */
+ if (isolated)
+ high_pfn = max(high_pfn, pfn);
+ }
+ spin_unlock_irqrestore(&zone->lock, flags);
+
+ cc->free_pfn = high_pfn;
+ cc->nr_freepages = nr_freepages;
+}
+
+/* Update the number of anon and file isolated pages in the zone) */
+void update_zone_isolated(struct zone *zone, struct compact_control *cc)
+{
+ struct page *page;
+ unsigned int count[NR_LRU_LISTS] = { 0, };
+
+ list_for_each_entry(page, &cc->migratepages, lru) {
+ int lru = page_lru_base_type(page);
+ count[lru]++;
+ }
+
+ cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
+ cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon);
+ __mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file);
+}
+
+/*
+ * Isolate all pages that can be migrated from the block pointed to by
+ * the migrate scanner within compact_control.
+ */
+static unsigned long isolate_migratepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ unsigned long low_pfn, end_pfn;
+ struct list_head *migratelist;
+
+ low_pfn = cc->migrate_pfn;
+ migratelist = &cc->migratepages;
+
+ /* Do not scan outside zone boundaries */
+ if (low_pfn < zone->zone_start_pfn)
+ low_pfn = zone->zone_start_pfn;
+
+ /* Setup to scan one block but not past where we are migrating to */
+ end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
+
+ /* Do not cross the free scanner or scan within a memory hole */
+ if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
+ cc->migrate_pfn = end_pfn;
+ return 0;
+ }
+
+ migrate_prep();
+
+ /* Time to isolate some pages for migration */
+ spin_lock_irq(&zone->lru_lock);
+ for (; low_pfn < end_pfn; low_pfn++) {
+ struct page *page;
+ if (!pfn_valid_within(low_pfn))
+ continue;
+
+ /* Get the page and skip if free */
+ page = pfn_to_page(low_pfn);
+ if (PageBuddy(page)) {
+ low_pfn += (1 << page_order(page)) - 1;
+ continue;
+ }
+
+ if (!PageLRU(page) || PageUnevictable(page))
+ continue;
+
+ /* Try isolate the page */
+ if (__isolate_lru_page(page, ISOLATE_BOTH, 0) == 0) {
+ del_page_from_lru_list(zone, page, page_lru(page));
+ list_add(&page->lru, migratelist);
+ mem_cgroup_del_lru(page);
+ cc->nr_migratepages++;
+ }
+
+ /* Avoid isolating too much */
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
+ break;
+ }
+
+ update_zone_isolated(zone, cc);
+
+ spin_unlock_irq(&zone->lru_lock);
+ cc->migrate_pfn = low_pfn;
+
+ return cc->nr_migratepages;
+}
+
+/*
+}
+
+/*
+ * We cannot control nr_migratepages and nr_freepages fully when migration is
+ * running as migrate_pages() has no knowledge of compact_control. When
+ * migration is complete, we count the number of pages on the lists by hand.
+ */
+static void update_nr_listpages(struct compact_control *cc)
+{
+ int nr_migratepages = 0;
+ int nr_freepages = 0;
+ struct page *page;
+ list_for_each_entry(page, &cc->migratepages, lru)
+ nr_migratepages++;
+ list_for_each_entry(page, &cc->freepages, lru)
+ nr_freepages++;
+
+ cc->nr_migratepages = nr_migratepages;
+ cc->nr_freepages = nr_freepages;
+}
+
+static inline int compact_finished(struct zone *zone,
+ struct compact_control *cc)
+{
+ /* Compaction run completes if the migrate and free scanner meet */
+ if (cc->free_pfn <= cc->migrate_pfn)
+ return COMPACT_COMPLETE;
+
+ return COMPACT_INCOMPLETE;
+}
+
+static int compact_zone(struct zone *zone, struct compact_control *cc)
+{
+ int ret = COMPACT_INCOMPLETE;
+
+ /* Setup to move all movable pages to the end of the zone */
+ cc->migrate_pfn = zone->zone_start_pfn;
+ cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
+ cc->free_pfn &= ~(pageblock_nr_pages-1);
+
+ for (; ret == COMPACT_INCOMPLETE; ret = compact_finished(zone, cc)) {
+ unsigned long nr_migrate, nr_remaining;
+ if (!isolate_migratepages(zone, cc))
+ continue;
+
+ nr_migrate = cc->nr_migratepages;
+ migrate_pages(&cc->migratepages, compaction_alloc,
+ (unsigned long)cc, 0);
+ update_nr_listpages(cc);
+ nr_remaining = cc->nr_migratepages;
+
+ count_vm_event(COMPACTBLOCKS);
+ count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
+ if (nr_remaining)
+ count_vm_events(COMPACTPAGEFAILED, nr_remaining);
+
+ /* Release LRU pages not migrated */
+ if (!list_empty(&cc->migratepages)) {
+ putback_lru_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ }
+
+ mod_zone_page_state(zone, NR_ISOLATED_ANON, -cc->nr_anon);
+ mod_zone_page_state(zone, NR_ISOLATED_FILE, -cc->nr_file);
+ }
+
+ /* Release free pages and check accounting */
+ cc->nr_freepages -= release_freepages(&cc->freepages);
+ VM_BUG_ON(cc->nr_freepages != 0);
+
+ return ret;
+}
+
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8deb9d0..6d57154 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1168,6 +1168,43 @@ void split_page(struct page *page, unsigned int order)
set_page_refcounted(page + i);
}
+/* Similar to split_page except the page is already free */
+int split_free_page(struct page *page)
+{
+ unsigned int order;
+ unsigned long watermark;
+ struct zone *zone;
+
+ BUG_ON(!PageBuddy(page));
+
+ zone = page_zone(page);
+ order = page_order(page);
+
+ /* Obey watermarks or the system could deadlock */
+ watermark = low_wmark_pages(zone) + (1 << order);
+ if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+ return 0;
+
diff --git a/mm/vmstat.c b/mm/vmstat.c
index fa5975c..0a14d22 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -889,6 +889,11 @@ static const char * const vmstat_text[] = {
"allocstall",
"pgrotated",
+
+ "compact_blocks_moved",
+ "compact_pages_moved",
+ "compact_pagemigrate_failed",
+
#ifdef CONFIG_HUGETLB_PAGE
"htlb_buddy_alloc_success",
"htlb_buddy_alloc_fail",
Mel Gorman
being able to hot-remove memory. The main users of page migration such as
sys_move_pages(), sys_migrate_pages() and cpuset process migration are
only beneficial on NUMA so it makes sense.
As memory compaction will operate within a zone and is useful on both NUMA
and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the
user selects CONFIG_COMPACTION as an option.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Reviewed-by: Christoph Lameter <c...@linux-foundation.org>
Reviewed-by: Rik van Riel <ri...@redhat.com>
---
mm/Kconfig | 20 ++++++++++++++++----
1 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index 17b8947..b1c2781 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -168,17 +168,29 @@ config SPLIT_PTLOCK_CPUS
default "4"
#
+# support for memory compaction
+config COMPACTION
+ bool "Allow for memory compaction"
+ def_bool y
+ select MIGRATION
+ depends on EXPERIMENTAL && HUGETLBFS
+ help
+ Allows the compaction of memory for the allocation of huge pages.
+
+#
# support for page migration
#
config MIGRATION
bool "Page migration"
def_bool y
- depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
+ depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
help
Allows the migration of the physical location of pages of processes
- while the virtual addresses are not changed. This is useful for
- example on NUMA systems to put pages nearer to the processors accessing
- the page.
+ while the virtual addresses are not changed. This is useful in
+ two situations. The first is on NUMA systems to put pages nearer
+ to the processors accessing. The second is when allocating huge
+ pages as migration can relocate pages to satisfy a huge page
+ allocation instead of reclaiming.
config PHYS_ADDR_T_64BIT
def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
Mel Gorman
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Reviewed-by: Christoph Lameter <c...@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki....@jp.fujitsu.com>
---
Documentation/filesystems/proc.txt | 45 +++++++++++++++++++++++++++++++++++-
1 files changed, 44 insertions(+), 1 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 0d07513..1829dfb 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -430,6 +430,7 @@ Table 1-5: Kernel info in /proc
modules List of loaded modules
mounts Mounted filesystems
net Networking info (see text)
+ pagetypeinfo Additional page allocator information (see text) (2.5)
partitions Table of partitions known to the system
pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
decoupled by lspci (2.4)
@@ -584,7 +585,7 @@ Node 0, zone DMA 0 4 5 4 4 3 ...
Node 0, zone Normal 1 0 0 1 101 8 ...
Node 0, zone HighMem 2 0 0 1 1 0 ...
-Memory fragmentation is a problem under some workloads, and buddyinfo is a
+External fragmentation is a problem under some workloads, and buddyinfo is a
useful tool for helping diagnose these problems. Buddyinfo will give you a
clue as to how big an area you can safely allocate, or why a previous
allocation failed.
@@ -594,6 +595,48 @@ available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...
+More information relevant to external fragmentation can be found in
+pagetypeinfo.
+
+> cat /proc/pagetypeinfo
+Page block order: 9
+Pages per block: 512
+
+Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
+Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
+Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
+Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
+Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
+Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
+Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
+Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
+Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
+Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
+Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
+
+Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
+Node 0, zone DMA 2 0 5 1 0
+Node 0, zone DMA32 41 6 967 2 0
+
+Fragmentation avoidance in the kernel works by grouping pages of different
+migrate types into the same contiguous regions of memory called page blocks.
+A page block is typically the size of the default hugepage size e.g. 2MB on
+X86-64. By keeping pages grouped based on their ability to move, the kernel
+can reclaim pages within a page block to satisfy a high-order allocation.
+
+The pagetypinfo begins with information on the size of a page block. It
+then gives the same type of information as buddyinfo except broken down
+by migrate-type and finishes with details on how many page blocks of each
+type exist.
+
+If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
+from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
+make an estimate of the likely number of huge pages that can be allocated
+at a given point in time. All the "Movable" blocks should be allocatable
+unless memory has been mlock()'d. Some of the Reclaimable blocks should
+also be allocatable although a lot of filesystem metadata may have to be
+reclaimed to achieve this.
+
..............................................................................
meminfo:
Mel Gorman
written to, each zone in that node is compacted. The intention that this
would be used by something like a job scheduler in a batch system before
a job starts so that the job can allocate the maximum number of
hugepages without significant start-up cost.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
---
drivers/base/node.c | 3 +++
include/linux/compaction.h | 16 ++++++++++++++++
mm/compaction.c | 23 +++++++++++++++++++++++
3 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 7012279..2333c9d 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -15,6 +15,7 @@
#include <linux/cpu.h>
#include <linux/device.h>
#include <linux/swap.h>
+#include <linux/compaction.h>
static struct sysdev_class node_class = {
.name = "node",
@@ -239,6 +240,8 @@ int register_node(struct node *node, int num, struct node *parent)
scan_unevictable_register_node(node);
hugetlb_register_node(node);
+
+ compaction_register_node(node);
}
return error;
}
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index facaa3d..6a2eefd 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -10,4 +10,20 @@ extern int sysctl_compaction_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos);
#endif /* CONFIG_COMPACTION */
+#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+extern int compaction_register_node(struct node *node);
+extern void compaction_unregister_node(struct node *node);
+
+#else
+
+static inline int compaction_register_node(struct node *node)
+{
+ return 0;
+}
+
+static inline void compaction_unregister_node(struct node *node)
+{
+}
+#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
+
#endif /* _LINUX_COMPACTION_H */
diff --git a/mm/compaction.c b/mm/compaction.c
index 22f223f..02579c2 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -12,6 +12,7 @@
#include <linux/compaction.h>
#include <linux/mm_inline.h>
#include <linux/sysctl.h>
+#include <linux/sysfs.h>
#include "internal.h"
/*
@@ -405,3 +406,25 @@ int sysctl_compaction_handler(struct ctl_table *table, int write,
return 0;
}
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+ssize_t sysfs_compact_node(struct sys_device *dev,
+ struct sysdev_attribute *attr,
+ const char *buf, size_t count)
+{
+ compact_node(dev->id);
+
+ return count;
+}
+static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
+
+int compaction_register_node(struct node *node)
+{
+ return sysdev_create_file(&node->sysdev, &attr_compact);
+}
+
+void compaction_unregister_node(struct node *node)
+{
+ return sysdev_remove_file(&node->sysdev, &attr_compact);
+}
+#endif /* CONFIG_SYSFS && CONFIG_NUMA */
Mel Gorman
use-after-free errors in anon_vma. The problem appears to be that between
the page being isolated from the LRU and rcu_read_lock() being taken, the
mapcount of the page dropped to 0 and the anon_vma was freed. This patch
skips the migration of anon pages that are not mapped by anyone.
Signed-off-by: Mel Gorman <m...@csn.ul.ie>
---
mm/migrate.c | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index 63addfa..1ce6a2f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -606,6 +606,16 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
* just care Anon page here.
*/
if (PageAnon(page)) {
+ /*
+ * If the page has no mappings any more, just bail. An
+ * unmapped anon page is likely to be freed soon but worse,
+ * it's possible its anon_vma disappeared between when
+ * the page was isolated and when we reached here while
+ * the RCU lock was not held
+ */
+ if (!page_mapcount(page))
+ goto uncharge;
+
rcu_read_lock();
rcu_locked = 1;
anon_vma = page_anon_vma(page);
Christoph Lameter
> > Oh there are numerous ZONE_DMA pressure issues if you have ancient /
> > screwed up hardware that can only operate on DMA or DMA32 memory.
> >
>
> I've never ran into the issue. I was under the impression that the only
> device that might care these days are floopy disks.
Kame-san had an issue a year or so ago.
Christoph Lameter
Mel Gorman
> On Tue, 16 Feb 2010, Mel Gorman wrote:
>
> > > Oh there are numerous ZONE_DMA pressure issues if you have ancient /
> > > screwed up hardware that can only operate on DMA or DMA32 memory.
> > >
> >
> > I've never ran into the issue. I was under the impression that the only
> > device that might care these days are floopy disks.
>
> Kame-san had an issue a year or so ago.
>
Will add it as a potential follow-on then. I consider Unevictable more
important than zone-pressure issues. Neither are going to be done in the
first pass. It's complex enough as it is and I'm more concerned with
getting teh page migration anon_vma snag ironed out. Can you review the
patches related to page migration in v3 please and see what you think?
You are much more familiar with the intent of that area than I.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
KAMEZAWA Hiroyuki
Christoph Lameter <c...@linux-foundation.org> wrote:
> On Tue, 16 Feb 2010, Mel Gorman wrote:
>
> > > Oh there are numerous ZONE_DMA pressure issues if you have ancient /
> > > screwed up hardware that can only operate on DMA or DMA32 memory.
> > >
> >
> > I've never ran into the issue. I was under the impression that the only
> > device that might care these days are floopy disks.
>
> Kame-san had an issue a year or so ago.
>
Yes. But my customer doesn't use the newest things...
In server area, recent hardware(64bit) and drivers tend not to cause the issue.
I'm not sure there are some driver which still set their DMA mask wrong and
require bounce buffer. But I guess that I'll have to see DMA-zone issue in
customer support still in (early) RHEL6.
Considering other area, I hear OOM-issue from notebook/desktop users, they don't
equip swap. I think some of devices are still 32bit if 64bit isn't required for them.
I wonder problems on lower-zone still exists for 32bit devices users.
In the view point as kernels for x86-32 still support ZONE_DMA
for ISA bus...we shouldn't assume there are no legacy.
But yes, it may not be very important to implement inter-zone moving. It's not
for compaction, but just for memory-reclaim. And it has some complication.
Thanks,
-Kame
KAMEZAWA Hiroyuki
Mel Gorman <m...@csn.ul.ie> wrote:
> rmap_walk_anon() does not use page_lock_anon_vma() for looking up and
> locking an anon_vma and it does not appear to have sufficient locking to
> ensure the anon_vma does not disappear from under it.
>
> This patch copies an approach used by KSM to take a reference on the
> anon_vma while pages are being migrated. This should prevent rmap_walk()
> running into nasty surprises later because anon_vma has been freed.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
I have no objection to this direction. But after this patch, you can remove
rcu_read_lock()/unlock() in unmap_and_move().
ruc_read_lock() is for guarding against anon_vma replacement.
Thanks,
-Kame
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majo...@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"do...@kvack.org"> em...@kvack.org </a>
KAMEZAWA Hiroyuki
Mel Gorman <m...@csn.ul.ie> wrote:
> CONFIG_MIGRATION currently depends on CONFIG_NUMA or on the architecture
> being able to hot-remove memory. The main users of page migration such as
> sys_move_pages(), sys_migrate_pages() and cpuset process migration are
> only beneficial on NUMA so it makes sense.
>
> As memory compaction will operate within a zone and is useful on both NUMA
> and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the
> user selects CONFIG_COMPACTION as an option.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> Reviewed-by: Christoph Lameter <c...@linux-foundation.org>
> Reviewed-by: Rik van Riel <ri...@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezaw...@jp.fujitsu.com>
But see below.
> ---
> mm/Kconfig | 20 ++++++++++++++++----
> 1 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 17b8947..b1c2781 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -168,17 +168,29 @@ config SPLIT_PTLOCK_CPUS
> default "4"
>
> #
> +# support for memory compaction
> +config COMPACTION
> + bool "Allow for memory compaction"
> + def_bool y
> + select MIGRATION
> + depends on EXPERIMENTAL && HUGETLBFS
> + help
> + Allows the compaction of memory for the allocation of huge pages.
> +
I think
+ depends on MMU
Thanks,
-Kame
> +#
> # support for page migration
> #
> config MIGRATION
> bool "Page migration"
> def_bool y
> - depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
> + depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
> help
> Allows the migration of the physical location of pages of processes
> - while the virtual addresses are not changed. This is useful for
> - example on NUMA systems to put pages nearer to the processors accessing
> - the page.
> + while the virtual addresses are not changed. This is useful in
> + two situations. The first is on NUMA systems to put pages nearer
> + to the processors accessing. The second is when allocating huge
> + pages as migration can relocate pages to satisfy a huge page
> + allocation instead of reclaiming.
>
> config PHYS_ADDR_T_64BIT
> def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
> --
> 1.6.5
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majo...@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"do...@kvack.org"> em...@kvack.org </a>
>
--
KAMEZAWA Hiroyuki
Mel Gorman <m...@csn.ul.ie> wrote:
> This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> value is written to the file, all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> Acked-by: Rik van Riel <ri...@redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezaw...@jp.fujitsu.com>
Nitpick:
Hmm.. Is this necessary if we have per-node trigger in sysfs ?
Thanks,
-Kame
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majo...@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"do...@kvack.org"> em...@kvack.org </a>
>
--
KAMEZAWA Hiroyuki
Doen't this mean failure of compaction ?
If there are memory hole, compaction of this area never be archieved.
If so, we should stop compaction of this area.
> +
> + page = pfn_to_page(blockpfn);
> + if (!PageBuddy(page))
> + continue;
> +
> + /* Found a free page, break it into order-0 pages */
> + isolated = split_free_page(page);
> + total_isolated += isolated;
> + for (i = 0; i < isolated; i++) {
> + list_add(&page->lru, freelist);
> + page++;
> + }
> +
> + /* If a page was split, advance to the end of it */
> + if (isolated)
> + blockpfn += isolated - 1;
> + }
> +
> + return total_isolated;
> +}
Hmm, I wonder ...how about setting migrate type of page block to be ISOLATED
at the end of this function ?
Then, no new page allocation occurs in this pageblock. And you don't have to
keep the list of free pages. free_page() does isolation.
I'm sorry I miss something.
break ?
> +
> + /* Get the page and skip if free */
> + page = pfn_to_page(low_pfn);
> + if (PageBuddy(page)) {
> + low_pfn += (1 << page_order(page)) - 1;
> + continue;
> + }
> +
> + if (!PageLRU(page) || PageUnevictable(page))
> +
break ? (compaction will not succeed if !PG_lru). I'm not sure
best-effort which can't readh goal is good or not. But conservative
approach will be better as the 1st version..
Thanks,
-Kame
Minchan Kim
> On Fri, Feb 19, 2010 at 01:58:44AM +0900, Minchan Kim wrote:
>> On Fri, 2010-02-12 at 12:00 +0000, Mel Gorman wrote:
>> > +/* Isolate free pages onto a private freelist. Must hold zone->lock */
>> > +static int isolate_freepages_block(struct zone *zone,
>>
>> return type 'int'?
>> I think we can't return signed value.
>>
>
> I don't understand your query. What's wrong with returning int?
It's just nitpick. I mean this functions doesn't return minus value.
Never mind.
I don't know such architecture until now.
Thanks for telling me.
How about adding the comment about that?
>
>> > +
>> > + /* Check the block is suitable for migration */
>> > + if (!suitable_migration_target(page))
>> > + continue;
>>
>> Dumb question.
>> suitable_migration_target considers three type's pages
>>
>> 1. free page and page's order >= pageblock_order
>> 2. free pages and pages's order < pageblock_order with movable page
>> 3. used page with movable
>>
>> I can understand 1 and 2 but can't 3. This function is for gathering
>> free page. How do you handle used page as free one?
>>
>> In addition, as I looked into isolate_freepages_block, it doesn't
>> consider 3 by PageBuddy check.
>>
>> I am confusing. Pz, correct me.
>>
>
> I'm afraid I don't understand your question. At the point
> suitable_migration_target() is called, the only concern is finding a pageblock
> of pages that should be scanned for free pages by isolate_freepages_block().
> What do you mean by "used page with movable" ?
After I looked into code, I understand it.
Thanks.
<snip>
>>> +/* Similar to split_page except the page is already free */
>> Sometime, this function changes pages's type to MIGRATE_MOVABLE.
>> I hope adding comment about that.
>>
>
> There is a comment within the function about it. Do you want it moved to
> here?
If you don't mind, I hope so. :)
That's because you wrote down only "except the page is already free" in
function description. So I thought it's only difference with split_page at first
glance. I think information that setting MIGRATE_MOVABLE is important.
Pz, thinks it as just nitpick.
Thanks, Mel.
--
Kind regards,
Minchan Kim
Minchan Kim
> This patch adds documentation for /proc/pagetypeinfo.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> Reviewed-by: Christoph Lameter <c...@linux-foundation.org>
> Reviewed-by: KOSAKI Motohiro <kosaki....@jp.fujitsu.com>
--
Kind regards,
Minchan Kim
Minchan Kim
> takes the allocation size into account. For the most part, the huge page
> size will be the size of interest but not necessarily so it is exported
> on a per-order and per-zone basis via /proc/unusable_index.
>
> The index is a value between 0 and 1. It can be expressed as a
> percentage by multiplying by 100 as documented in
> Documentation/filesystems/proc.txt.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
--
Kind regards,
Minchan Kim
Minchan Kim
> This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> value is written to the file, all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
>
Reviewed-by: Minchan Kim <minchan.kim>
Minchan Kim
> given size would fail. The index indicates whether an allocation failure is
> due to a lack of memory (values towards 0) or due to external fragmentation
> (value towards 1). For the most part, the huge page size will be the size
> of interest but not necessarily so it is exported on a per-order and per-zone
> basis via /proc/pagetypeinfo.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
--
Kind regards,
Minchan Kim
Minchan Kim
> value is written to the file, all zones are compacted. The expected user
> of such a trigger is a job scheduler that prepares the system before the
> target application runs.
>
> Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> Acked-by: Rik van Riel <ri...@redhat.com>
--
Kind regards,
Minchan Kim
Mel Gorman
> On Thu, 18 Feb 2010 18:02:31 +0000
> Mel Gorman <m...@csn.ul.ie> wrote:
>
> > rmap_walk_anon() does not use page_lock_anon_vma() for looking up and
> > locking an anon_vma and it does not appear to have sufficient locking to
> > ensure the anon_vma does not disappear from under it.
> >
> > This patch copies an approach used by KSM to take a reference on the
> > anon_vma while pages are being migrated. This should prevent rmap_walk()
> > running into nasty surprises later because anon_vma has been freed.
> >
> > Signed-off-by: Mel Gorman <m...@csn.ul.ie>
>
> I have no objection to this direction. But after this patch, you can remove
> rcu_read_lock()/unlock() in unmap_and_move().
> ruc_read_lock() is for guarding against anon_vma replacement.
>
Thanks. I expected that would be the case but was going to leave at
least one kernel release between when compaction went in and I did that.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Mel Gorman
Agreed. Thanks
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Mel Gorman
> On Thu, 18 Feb 2010 18:02:39 +0000
> Mel Gorman <m...@csn.ul.ie> wrote:
>
> > This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> > value is written to the file, all zones are compacted. The expected user
> > of such a trigger is a job scheduler that prepares the system before the
> > target application runs.
> >
> > Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> > Acked-by: Rik van Riel <ri...@redhat.com>
>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezaw...@jp.fujitsu.com>
>
> Nitpick:
> Hmm.. Is this necessary if we have per-node trigger in sysfs ?
>
What does !NUMA do?
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Mel Gorman
Nope. We're isolating free pages as a migration target here, not a
source. If it finds a hole, move on to the next page. If necessary, the
next block will be moved to later.
> If there are memory hole, compaction of this area never be archieved.
> If so, we should stop compaction of this area.
>
Only half of the block might be in a hole so it's still worth checking
for free pages.
>
> > +
> > + page = pfn_to_page(blockpfn);
> > + if (!PageBuddy(page))
> > + continue;
> > +
> > + /* Found a free page, break it into order-0 pages */
> > + isolated = split_free_page(page);
> > + total_isolated += isolated;
> > + for (i = 0; i < isolated; i++) {
> > + list_add(&page->lru, freelist);
> > + page++;
> > + }
> > +
> > + /* If a page was split, advance to the end of it */
> > + if (isolated)
> > + blockpfn += isolated - 1;
> > + }
> > +
> > + return total_isolated;
> > +}
>
> Hmm, I wonder ...how about setting migrate type of page block to be ISOLATED
> at the end of this function ?
> Then, no new page allocation occurs in this pageblock. And you don't have to
> keep the list of free pages. free_page() does isolation.
>
Even if the block is marked ISOLATED, I would still have to move the
already-free pages between buddy lists. Targetting later for allocation
would then be slightly trickier as I'd have to scan the buddy lists. I
don't think it would be better overall as there would still be a lot of
messing with lists.
What if the whole was at the start of the page block? In the huge page
context, there is a strong chance that half a pageblock is worthless but
maybe it's useful in other contexts.
> > +
> > + /* Get the page and skip if free */
> > + page = pfn_to_page(low_pfn);
> > + if (PageBuddy(page)) {
> > + low_pfn += (1 << page_order(page)) - 1;
> > + continue;
> > + }
> > +
> > + if (!PageLRU(page) || PageUnevictable(page))
> > +
> break ? (compaction will not succeed if !PG_lru). I'm not sure
> best-effort which can't readh goal is good or not. But conservative
> approach will be better as the 1st version..
>
Well, lets say we are migrating from a MIGRATE_RECLAIMABLE block. That
block will not be freed for a huge page allocation, but it helps
fragmentation avoidance.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Mel Gorman
> On Fri, Feb 19, 2010 at 2:34 AM, Mel Gorman <m...@csn.ul.ie> wrote:
> > On Fri, Feb 19, 2010 at 01:58:44AM +0900, Minchan Kim wrote:
> >> On Fri, 2010-02-12 at 12:00 +0000, Mel Gorman wrote:
> >> > +/* Isolate free pages onto a private freelist. Must hold zone->lock */
> >> > +static int isolate_freepages_block(struct zone *zone,
> >>
> >> return type 'int'?
> >> I think we can't return signed value.
> >>
> >
> > I don't understand your query. What's wrong with returning int?
>
> It's just nitpick. I mean this functions doesn't return minus value.
> Never mind.
>
> >
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ struct list_head *freelist)
> >> > +{
> >> > + ￜ unsigned long zone_end_pfn, end_pfn;
> >> > + ￜ int total_isolated = 0;
> >> > +
> >> > + ￜ /* Get the last PFN we should scan for free pages at */
> >> > + ￜ zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
> >> > + ￜ end_pfn = blockpfn + pageblock_nr_pages;
> >> > + ￜ if (end_pfn > zone_end_pfn)
> >> > + ￜ ￜ ￜ ￜ ￜ end_pfn = zone_end_pfn;
> >> > +
> >> > + ￜ /* Isolate free pages. This assumes the block is valid */
> >> > + ￜ for (; blockpfn < end_pfn; blockpfn++) {
> >> > + ￜ ￜ ￜ ￜ ￜ struct page *page;
> >> > + ￜ ￜ ￜ ￜ ￜ int isolated, i;
> >> > +
> >> > + ￜ ￜ ￜ ￜ ￜ if (!pfn_valid_within(blockpfn))
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ continue;
> >> > +
> >> > + ￜ ￜ ￜ ￜ ￜ page = pfn_to_page(blockpfn);
> >> > + ￜ ￜ ￜ ￜ ￜ if (!PageBuddy(page))
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ continue;
> >> > +
> >> > + ￜ ￜ ￜ ￜ ￜ /* Found a free page, break it into order-0 pages */
> >> > + ￜ ￜ ￜ ￜ ￜ isolated = split_free_page(page);
> >> > + ￜ ￜ ￜ ￜ ￜ total_isolated += isolated;
> >> > + ￜ ￜ ￜ ￜ ￜ for (i = 0; i < isolated; i++) {
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ list_add(&page->lru, freelist);
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ page++;
> >> > + ￜ ￜ ￜ ￜ ￜ }
> >> > + ￜ ￜ ￜ ￜ ￜ blockpfn += isolated - 1;
> >
> > Incidentally, this line is wrong but will be fixed in line 3. If
> > split_free_page() fails, it causes an infinite loop.
> >
> >> > +
> >> > + ￜ return total_isolated;
> >> > +}
> >> > +
> >> > +/* Returns 1 if the page is within a block suitable for migration to */
> >> > +static int suitable_migration_target(struct page *page)
> >> > +{
> >> > + ￜ if (PageBuddy(page) && page_order(page) >= pageblock_order)
> >> > + ￜ ￜ ￜ ￜ ￜ return 1;
> >> > +
> >> > + ￜ /* If the block is MIGRATE_MOVABLE, allow migration */
> >> > + ￜ if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)
> >> > + ￜ ￜ ￜ ￜ ￜ return 1;
> >> > +
> >> > + ￜ /* Otherwise skip the block */
> >> > + ￜ return 0;
> >> > +}
> >> > +
> >> > +/*
> >> > + * Based on information in the current compact_control, find blocks
> >> > + * suitable for isolating free pages from
> >> > + */
> >> > +static void isolate_freepages(struct zone *zone,
> >> > +{
> >> > + ￜ struct page *page;
> >> > + ￜ unsigned long high_pfn, low_pfn, pfn;
> >> > + ￜ unsigned long flags;
> >> > + ￜ int nr_freepages = cc->nr_freepages;
> >> > + ￜ struct list_head *freelist = &cc->freepages;
> >> > +
> >> > + ￜ pfn = cc->free_pfn;
> >> > + ￜ low_pfn = cc->migrate_pfn + pageblock_nr_pages;
> >> > + ￜ high_pfn = low_pfn;
> >> > +
> >> > + ￜ /*
> >> > + ￜ ￜ* Isolate free pages until enough are available to migrate the
> >> > + ￜ ￜ* pages on cc->migratepages. We stop searching if the migrate
> >> > + ￜ ￜ* and free page scanners meet or enough free pages are isolated.
> >> > + ￜ ￜ*/
> >> > + ￜ spin_lock_irqsave(&zone->lock, flags);
> >> > + ￜ for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ pfn -= pageblock_nr_pages) {
> >> > + ￜ ￜ ￜ ￜ ￜ int isolated;
> >> > +
> >> > + ￜ ￜ ￜ ￜ ￜ if (!pfn_valid(pfn))
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ continue;
> >> > +
> >> > + ￜ ￜ ￜ ￜ ￜ /* Check for overlapping nodes/zones */
> >> > + ￜ ￜ ￜ ￜ ￜ page = pfn_to_page(pfn);
> >> > + ￜ ￜ ￜ ￜ ￜ if (page_zone(page) != zone)
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ continue;
> >>
> >> We are progressing backward by physical page order in a zone.
> >> If we meet crossover between zone, Why are we going backward
> >> continuously? Before it happens, migration and free scanner would meet.
> >> Am I miss something?
> >>
> >
> > I was considering a situation like the following
> >
> >
> > DMA ￜ ￜ ￜ ￜDMA ￜ ￜ ￜ ￜ ￜDMA
> > 0-1023 ￜ ￜ 1024-2047 ￜ ￜ2048-4096
> >
> > In that case, a PFN scanner can enter a new node and zone but the migrate
> > and free scanners have not necessarily met. This configuration is *extremely*
> > rare but it happens on messed-up LPAR configurations on POWER.
>
> I don't know such architecture until now.
> Thanks for telling me.
> How about adding the comment about that?
>
Sure
> >
> >> > +
> >> > + ￜ ￜ ￜ ￜ ￜ /* Check the block is suitable for migration */
> >> > + ￜ ￜ ￜ ￜ ￜ if (!suitable_migration_target(page))
> >> > + ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ ￜ continue;
> >>
> >> Dumb question.
> >> suitable_migration_target considers three type's pages
> >>
> >> 1. free page and page's order >= pageblock_order
> >> 2. free pages and pages's order < pageblock_order with movable page
> >> 3. used page with movable
> >>
> >> I can understand 1 and 2 but can't 3. This function is for gathering
> >> free page. How do you handle used page as free one?
> >>
> >> In addition, as I looked into isolate_freepages_block, it doesn't
> >> consider 3 by PageBuddy check.
> >>
> >> I am confusing. Pz, correct me.
> >>
> >
> > I'm afraid I don't understand your question. At the point
> > suitable_migration_target() is called, the only concern is finding a pageblock
> > of pages that should be scanned for free pages by isolate_freepages_block().
> > What do you mean by "used page with movable" ?
>
> After I looked into code, I understand it.
> Thanks.
>
> <snip>
> >>> +/* Similar to split_page except the page is already free */
> >> Sometime, this function changes pages's type to MIGRATE_MOVABLE.
> >> I hope adding comment about that.
> >>
> >
> > There is a comment within the function about it. Do you want it moved to
> > here?
>
> If you don't mind, I hope so. :)
>
Done.
> That's because you wrote down only "except the page is already free" in
> function description. So I thought it's only difference with split_page at first
> glance. I think information that setting MIGRATE_MOVABLE is important.
>
> Pz, thinks it as just nitpick.
No, it's a fair point. I can see how it could trip someone up.
Thanks
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Greg KH
> This patch adds a per-node sysfs file called compact. When the file is
> written to, each zone in that node is compacted. The intention that this
> would be used by something like a job scheduler in a batch system before
> a job starts so that the job can allocate the maximum number of
> hugepages without significant start-up cost.
As you are adding sysfs files, can you please also add documentation for
the file in Documentation/ABI/ ?
thanks,
greg k-h
Mel Gorman
> On Thu, Feb 18, 2010 at 06:02:40PM +0000, Mel Gorman wrote:
> > This patch adds a per-node sysfs file called compact. When the file is
> > written to, each zone in that node is compacted. The intention that this
> > would be used by something like a job scheduler in a batch system before
> > a job starts so that the job can allocate the maximum number of
> > hugepages without significant start-up cost.
>
> As you are adding sysfs files, can you please also add documentation for
> the file in Documentation/ABI/ ?
>
I looked at this before and hit a wall and then forgot about it. I couldn't
find *where* I should document it at the time. There isn't a sysfs-devices-node
file to add to and much (all?) of what is in that branch appears undocumented.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Greg KH
> On Fri, Feb 19, 2010 at 06:53:59AM -0800, Greg KH wrote:
> > On Thu, Feb 18, 2010 at 06:02:40PM +0000, Mel Gorman wrote:
> > > This patch adds a per-node sysfs file called compact. When the file is
> > > written to, each zone in that node is compacted. The intention that this
> > > would be used by something like a job scheduler in a batch system before
> > > a job starts so that the job can allocate the maximum number of
> > > hugepages without significant start-up cost.
> >
> > As you are adding sysfs files, can you please also add documentation for
> > the file in Documentation/ABI/ ?
> >
>
> I looked at this before and hit a wall and then forgot about it. I couldn't
> find *where* I should document it at the time. There isn't a sysfs-devices-node
> file to add to and much (all?) of what is in that branch appears undocumented.
Well, you can always just document what you add, or you can document the
existing stuff as well. It's your choice :)
thanks,
greg k-h
Mel Gorman
> On Fri, Feb 19, 2010 at 03:28:30PM +0000, Mel Gorman wrote:
> > On Fri, Feb 19, 2010 at 06:53:59AM -0800, Greg KH wrote:
> > > On Thu, Feb 18, 2010 at 06:02:40PM +0000, Mel Gorman wrote:
> > > > This patch adds a per-node sysfs file called compact. When the file is
> > > > written to, each zone in that node is compacted. The intention that this
> > > > would be used by something like a job scheduler in a batch system before
> > > > a job starts so that the job can allocate the maximum number of
> > > > hugepages without significant start-up cost.
> > >
> > > As you are adding sysfs files, can you please also add documentation for
> > > the file in Documentation/ABI/ ?
> > >
> >
> > I looked at this before and hit a wall and then forgot about it. I couldn't
> > find *where* I should document it at the time. There isn't a sysfs-devices-node
> > file to add to and much (all?) of what is in that branch appears undocumented.
>
> Well, you can always just document what you add, or you can document the
> existing stuff as well. It's your choice :)
>
Fair point!
I've taken note to document what's in there over time. For the moment,
is this a reasonable start? I'll split it into two patches but the end
result will be the same.
diff --git a/Documentation/ABI/testing/sysfs-devices-node b/Documentation/ABI/testing/sysfs-devices-node
new file mode 100644
index 0000000..1ee348b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-node
@@ -0,0 +1,15 @@
+What: /sys/devices/system/node/nodeX
+Date: October 2002
+Contact: Linux Memory Management list <linu...@kvack.org>
+Description:
+ When CONFIG_NUMA is enabled, this is a directory containing
+ information on node X such as what CPUs are local to the
+ node.
+
+What: /sys/devices/system/node/nodeX/compact
+Date: February 2010
+Contact: Mel Gorman <m...@csn.ul.ie>
+Description:
+ When this file is written to, all memory within that node
+ will be compacted. When it completes, memory will be free
+ in as contiguous blocks as possible.
Mel Gorman
> On Fri, Feb 19, 2010 at 07:31:42AM -0800, Greg KH wrote:
> > On Fri, Feb 19, 2010 at 03:28:30PM +0000, Mel Gorman wrote:
> > > On Fri, Feb 19, 2010 at 06:53:59AM -0800, Greg KH wrote:
> > > > On Thu, Feb 18, 2010 at 06:02:40PM +0000, Mel Gorman wrote:
> > > > > This patch adds a per-node sysfs file called compact. When the file is
> > > > > written to, each zone in that node is compacted. The intention that this
> > > > > would be used by something like a job scheduler in a batch system before
> > > > > a job starts so that the job can allocate the maximum number of
> > > > > hugepages without significant start-up cost.
> > > >
> > > > As you are adding sysfs files, can you please also add documentation for
> > > > the file in Documentation/ABI/ ?
> > > >
> > >
> > > I looked at this before and hit a wall and then forgot about it. I couldn't
> > > find *where* I should document it at the time. There isn't a sysfs-devices-node
> > > file to add to and much (all?) of what is in that branch appears undocumented.
> >
> > Well, you can always just document what you add, or you can document the
> > existing stuff as well. It's your choice :)
> >
>
> Fair point!
>
> I've taken note to document what's in there over time. For the moment,
> is this a reasonable start? I'll split it into two patches but the end
> result will be the same.
>
Bah, as I hit send, I recognised my folly. The first entry should be in
stable/ and the second should be in testing/.
> diff --git a/Documentation/ABI/testing/sysfs-devices-node b/Documentation/ABI/testing/sysfs-devices-node
> new file mode 100644
> index 0000000..1ee348b
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-devices-node
> @@ -0,0 +1,15 @@
> +What: /sys/devices/system/node/nodeX
> +Date: October 2002
> +Contact: Linux Memory Management list <linu...@kvack.org>
> +Description:
> + When CONFIG_NUMA is enabled, this is a directory containing
> + information on node X such as what CPUs are local to the
> + node.
> +
> +What: /sys/devices/system/node/nodeX/compact
> +Date: February 2010
> +Contact: Mel Gorman <m...@csn.ul.ie>
> +Description:
> + When this file is written to, all memory within that node
> + will be compacted. When it completes, memory will be free
> + in as contiguous blocks as possible.
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majo...@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"do...@kvack.org"> em...@kvack.org </a>
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
Greg KH
> On Fri, Feb 19, 2010 at 03:51:17PM +0000, Mel Gorman wrote:
> > On Fri, Feb 19, 2010 at 07:31:42AM -0800, Greg KH wrote:
> > > On Fri, Feb 19, 2010 at 03:28:30PM +0000, Mel Gorman wrote:
> > > > On Fri, Feb 19, 2010 at 06:53:59AM -0800, Greg KH wrote:
> > > > > On Thu, Feb 18, 2010 at 06:02:40PM +0000, Mel Gorman wrote:
> > > > > > This patch adds a per-node sysfs file called compact. When the file is
> > > > > > written to, each zone in that node is compacted. The intention that this
> > > > > > would be used by something like a job scheduler in a batch system before
> > > > > > a job starts so that the job can allocate the maximum number of
> > > > > > hugepages without significant start-up cost.
> > > > >
> > > > > As you are adding sysfs files, can you please also add documentation for
> > > > > the file in Documentation/ABI/ ?
> > > > >
> > > >
> > > > I looked at this before and hit a wall and then forgot about it. I couldn't
> > > > find *where* I should document it at the time. There isn't a sysfs-devices-node
> > > > file to add to and much (all?) of what is in that branch appears undocumented.
> > >
> > > Well, you can always just document what you add, or you can document the
> > > existing stuff as well. It's your choice :)
> > >
> >
> > Fair point!
> >
> > I've taken note to document what's in there over time. For the moment,
> > is this a reasonable start? I'll split it into two patches but the end
> > result will be the same.
> >
>
> Bah, as I hit send, I recognised my folly. The first entry should be in
> stable/ and the second should be in testing/.
>
Heh, no problem, looks good to me, thanks for doing this.
greg k-h
Rik van Riel
> rmap_walk_anon() does not use page_lock_anon_vma() for looking up and
> locking an anon_vma and it does not appear to have sufficient locking to
> ensure the anon_vma does not disappear from under it.
>
> This patch copies an approach used by KSM to take a reference on the
> anon_vma while pages are being migrated. This should prevent rmap_walk()
> running into nasty surprises later because anon_vma has been freed.
>
Acked-by: Rik van Riel <ri...@redhat.com>
--
All rights reversed.
Rik van Riel
> use-after-free errors in anon_vma. The problem appears to be that between
> the page being isolated from the LRU and rcu_read_lock() being taken, the
> mapcount of the page dropped to 0 and the anon_vma was freed. This patch
> skips the migration of anon pages that are not mapped by anyone.
Rik van Riel
> size will be the size of interest but not necessarily so it is exported
>
> The index is a value between 0 and 1. It can be expressed as a
> percentage by multiplying by 100 as documented in
> Documentation/filesystems/proc.txt.
>
Rik van Riel
>
> Reviewed-by: Christoph Lameter<c...@linux-foundation.org>
Rik van Riel
> given size would fail. The index indicates whether an allocation failure is
> due to a lack of memory (values towards 0) or due to external fragmentation
> of interest but not necessarily so it is exported on a per-order and per-zone
>
> Signed-off-by: Mel Gorman<m...@csn.ul.ie>
Acked-by: Rik van Riel <ri...@redhat.com>
KAMEZAWA Hiroyuki
Mel Gorman <m...@csn.ul.ie> wrote:
> On Fri, Feb 19, 2010 at 09:43:26AM +0900, KAMEZAWA Hiroyuki wrote:
> > On Thu, 18 Feb 2010 18:02:39 +0000
> > Mel Gorman <m...@csn.ul.ie> wrote:
> >
> > > This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
> > > value is written to the file, all zones are compacted. The expected user
> > > of such a trigger is a job scheduler that prepares the system before the
> > > target application runs.
> > >
> > > Signed-off-by: Mel Gorman <m...@csn.ul.ie>
> > > Acked-by: Rik van Riel <ri...@redhat.com>
> >
> > Reviewed-by: KAMEZAWA Hiroyuki <kamezaw...@jp.fujitsu.com>
> >
> > Nitpick:
> > Hmm.. Is this necessary if we have per-node trigger in sysfs ?
> >
>
> What does !NUMA do?
>
.... I missed that. please ignore my comment.
(And I missed that we already have famous trigger as drop_caches in sysctl..)
Thanks,
-Kame